Based on the original bug 1680361, comment #38:

In RHV conversion host, run:
$ yum downgrade libguestfs libguestfs-tools-c virt-v2v python-libguestfs,
brings interim version: 1.40.2-5.el7.1.bz1680361.v3.1.x86_64 (based on Derez fix).

Using this repo:
http://brew-task-repos.usersys.redhat.com/repos/scratch/rjones/libguestfs/1.40.2/5.el7.1.bz1680361.v3.1/

Error: 'RuntimeError: timed out waiting for transfer to finalize\n' no longer appeared.

I managed to run v2v migration, VMware->RHV ISCSI->FC, VDDK, for a single VM, with 20GB disk successfully.

This RHEL-7.7 bug can be moved to VERIFIED.

Verify the bug with builds:
virt-v2v-1.40.2-5.el7_7.2.x86_64
libguestfs-1.40.2-5.el7_7.2.x86_64
libvirt-4.5.0-23.el7_7.1.x86_64
qemu-kvm-rhev-2.12.0-33.el7_7.4.x86_64
nbdkit-1.8.0-1.el7.x86_64
VMware-vix-disklib-6.7.3-14389676.x86_64.tar.gz
RHV:4.3.6.5-0.1.el7
vdsm-4.30.30-1.el7ev.x86_64


Steps:
Scenario1:
1.1 Convert a rhel7 guest which has disk size more than 100GB from VMware host to rhv's FC domain on standalone v2v conversion server by virt-v2v
# virt-v2v -ic esx://root.75.219/?no_verify=1 rhv-4.3-150G -it vddk  -io vddk-libdir=/home/vmware-vix-disklib-distrib -io vddk-thumbprint=89:89:AE:6D:DE:B2:89:01:B0:CF:FC:D3:C8:A8:1A:5E:14:E4:B4:54 -o rhv-upload -oo rhv-cafile=/root/ca.pem -oo rhv-direct -oc https://hp-dl360eg8-03.lab.eng.pek2.redhat.com/ovirt-engine/api -op /tmp/rhvpasswd -os fc_data -b ovirtmgmt -oo rhv-cluster=FC --password-file /tmp/esxpw -of raw -oa preallocated
Exception AttributeError: "'module' object has no attribute 'dump_plugin'" in <module 'threading' from '/usr/lib64/python2.7/threading.pyc'> ignored
[   0.5] Opening the source -i libvirt -ic esx://root.75.219/?no_verify=1 rhv-4.3-150G -it vddk  -io vddk-libdir=/home/vmware-vix-disklib-distrib -io vddk-thumbprint=89:89:AE:6D:DE:B2:89:01:B0:CF:FC:D3:C8:A8:1A:5E:14:E4:B4:54
[   1.9] Creating an overlay to protect the source from being modified
nbdkit: error: VixDiskLib: VixDiskLibIsLegacyConnParams: the instance of VixDiskLibConnectParams is NOT allocated by VixDiskLib_AllocateConnectParams. The new features in 6.7 or later are not supported.
[   3.0] Opening the overlay
nbdkit: error: VixDiskLib: VixDiskLibIsLegacyConnParams: the instance of VixDiskLibConnectParams is NOT allocated by VixDiskLib_AllocateConnectParams. The new features in 6.7 or later are not supported.
[  25.9] Inspecting the overlay
[  60.8] Checking for sufficient free disk space in the guest
[  60.8] Estimating space required on target for each disk
[  60.8] Converting Red Hat Enterprise Linux Server 7.6 (Maipo) to run on KVM
virt-v2v: This guest has virtio drivers installed.
[ 224.8] Mapping filesystem data to avoid copying unused and blank areas
[ 225.2] Closing the overlay
[ 225.5] Assigning disks to buses
[ 225.5] Checking if the guest needs BIOS or UEFI to boot
[ 225.5] Initializing the target -o rhv-upload -oa preallocated -oc https://hp-dl360eg8-03.lab.eng.pek2.redhat.com/ovirt-engine/api -op /tmp/rhvpasswd -os fc_data
[ 227.0] Copying disk 1/1 to qemu URI json:{ "file.driver": "nbd", "file.path": "/var/tmp/rhvupload.MYycIT/nbdkit0.sock", "file.export": "/" } (raw)
nbdkit: error: VixDiskLib: VixDiskLibIsLegacyConnParams: the instance of VixDiskLibConnectParams is NOT allocated by VixDiskLib_AllocateConnectParams. The new features in 6.7 or later are not supported.
    (100.00/100%)
[4883.7] Creating output metadata
[4894.0] Finishing off

1.2 Power on guest and checkpoints of guest are passed

1.3 Convert a rhel7 guest which has disk size more than 100GB from VMware vCenter to rhv's iscsi data domain on standalone v2v conversion server by virt-v2v
 virt-v2v -ic vpx://root.73.141/data/10.73.75.219/?no_verify=1 -it vddk -io vddk-libdir=/home/vmware-vix-disklib-distrib -io  vddk-thumbprint=1F:97:34:5F:B6:C2:BA:66:46:CB:1A:71:76:7D:6B:50:1E:03:00:EA  rhv-4.3-150G -o rhv-upload -oo rhv-cafile=/root/ca.pem -oo rhv-direct -oc https://hp-dl360eg8-03.lab.eng.pek2.redhat.com/ovirt-engine/api -op /tmp/rhvpasswd -os iscsi_data -b ovirtmgmt -oo rhv-cluster=ISCSI --password-file /tmp/passwd -of raw -oa preallocated
Exception AttributeError: "'module' object has no attribute 'dump_plugin'" in <module 'threading' from '/usr/lib64/python2.7/threading.pyc'> ignored
[   0.5] Opening the source -i libvirt -ic vpx://root.73.141/data/10.73.75.219/?no_verify=1 rhv-4.3-150G -it vddk  -io vddk-libdir=/home/vmware-vix-disklib-distrib -io vddk-thumbprint=1F:97:34:5F:B6:C2:BA:66:46:CB:1A:71:76:7D:6B:50:1E:03:00:EA
[   2.5] Creating an overlay to protect the source from being modified
nbdkit: error: VixDiskLib: VixDiskLibIsLegacyConnParams: the instance of VixDiskLibConnectParams is NOT allocated by VixDiskLib_AllocateConnectParams. The new features in 6.7 or later are not supported.
[   3.9] Opening the overlay
nbdkit: error: VixDiskLib: VixDiskLibIsLegacyConnParams: the instance of VixDiskLibConnectParams is NOT allocated by VixDiskLib_AllocateConnectParams. The new features in 6.7 or later are not supported.
[   8.8] Inspecting the overlay
[  44.8] Checking for sufficient free disk space in the guest
[  44.8] Estimating space required on target for each disk
[  44.8] Converting Red Hat Enterprise Linux Server 7.6 (Maipo) to run on KVM
virt-v2v: This guest has virtio drivers installed.
[ 220.2] Mapping filesystem data to avoid copying unused and blank areas
[ 220.6] Closing the overlay
[ 220.9] Assigning disks to buses
[ 220.9] Checking if the guest needs BIOS or UEFI to boot
[ 220.9] Initializing the target -o rhv-upload -oa preallocated -oc https://hp-dl360eg8-03.lab.eng.pek2.redhat.com/ovirt-engine/api -op /tmp/rhvpasswd -os iscsi_data
[ 222.4] Copying disk 1/1 to qemu URI json:{ "file.driver": "nbd", "file.path": "/var/tmp/rhvupload.OBpy6z/nbdkit0.sock", "file.export": "/" } (raw)
nbdkit: error: VixDiskLib: VixDiskLibIsLegacyConnParams: the instance of VixDiskLibConnectParams is NOT allocated by VixDiskLib_AllocateConnectParams. The new features in 6.7 or later are not supported.
    (100.00/100%)
[5383.7] Creating output metadata
[5392.0] Finishing off


Scenario2:
2.1 Import the guest which has disk size more than 100GB from VMware on RHV GUI

Click import option on Virtual Machine interface-> input VMware host info to load the guest-> select the guest to import

2.2 The importing is finished without error,power on guest and checkpoints of guest are passed


Sceanrio3:
3.1 Convert a rhel7 guest which has disk size more than 100GB from VMware to rhv on rhv-node by virt-v2v(rhv-node and data domain belong to different datacenter)
# virt-v2v -ic esx://root.75.219/?no_verify=1 rhv-4.3-150G -it vddk  -io vddk-libdir=/home/vmware-vix-disklib-distrib -io vddk-thumbprint=89:89:AE:6D:DE:B2:89:01:B0:CF:FC:D3:C8:A8:1A:5E:14:E4:B4:54  -o rhv-upload -oo rhv-cafile=/home/ca.pem -oo rhv-direct -oc https://ibm-x3250m5-03.rhts.eng.pek2.redhat.com/ovirt-engine/api -op /tmp/rhvpasswd -os rhvh_data -b ovirtmgmt -oo rhv-cluster=rhvh --password-file /tmp/esxpw -of raw
Exception AttributeError: "'module' object has no attribute 'dump_plugin'" in <module 'threading' from '/usr/lib64/python2.7/threading.pyc'> ignored
[   0.3] Opening the source -i libvirt -ic esx://root.75.219/?no_verify=1 rhv-4.3-150G -it vddk  -io vddk-libdir=/home/vmware-vix-disklib-distrib -io vddk-thumbprint=89:89:AE:6D:DE:B2:89:01:B0:CF:FC:D3:C8:A8:1A:5E:14:E4:B4:54
[   1.8] Creating an overlay to protect the source from being modified
nbdkit: error: VixDiskLib: VixDiskLibIsLegacyConnParams: the instance of VixDiskLibConnectParams is NOT allocated by VixDiskLib_AllocateConnectParams. The new features in 6.7 or later are not supported.
[   2.8] Opening the overlay
libvirt needs authentication to connect to libvirt URI qemu:///system
(see also: http://libvirt.org/auth.html http://libvirt.org/uri.html)
Please enter your authentication name: test
Please enter your password: 
nbdkit: error: VixDiskLib: VixDiskLibIsLegacyConnParams: the instance of VixDiskLibConnectParams is NOT allocated by VixDiskLib_AllocateConnectParams. The new features in 6.7 or later are not supported.
[  11.2] Inspecting the overlay
[  40.0] Checking for sufficient free disk space in the guest
[  40.0] Estimating space required on target for each disk
[  40.0] Converting Red Hat Enterprise Linux Server 7.6 (Maipo) to run on KVM
virt-v2v: This guest has virtio drivers installed.
[ 186.0] Mapping filesystem data to avoid copying unused and blank areas
[ 186.3] Closing the overlay
[ 187.1] Assigning disks to buses
[ 187.1] Checking if the guest needs BIOS or UEFI to boot
[ 187.1] Initializing the target -o rhv-upload -oc https://ibm-x3250m5-03.rhts.eng.pek2.redhat.com/ovirt-engine/api -op /tmp/rhvpasswd -os rhvh_data
[ 188.4] Copying disk 1/1 to qemu URI json:{ "file.driver": "nbd", "file.path": "/var/tmp/rhvupload.aHfrRq/nbdkit0.sock", "file.export": "/" } (raw)
nbdkit: error: VixDiskLib: VixDiskLibIsLegacyConnParams: the instance of VixDiskLibConnectParams is NOT allocated by VixDiskLib_AllocateConnectParams. The new features in 6.7 or later are not supported.
    (100.00/100%)
[11289.8] Creating output metadata
[11301.0] Finishing off

3.2 Power on guest and checkpoints of guest are passed

In reply to comment #5:

I tried already several times, and also today, to run 20 VMs of 20GB on the exact same RHV/hosts,
that has virt-v2v-1.40.2-5.el7_7.1.x86_64.
Bug did not reproduce. Based on that I cannot verify the bug. In case the bug will occur, though the fix, i'll update this bug.

Correction to comment #7: the v2v MVware->RHV run was for 20 VMs with __100GB__ disk, 66% usage.

Because the bug happened with a low frequency and is hard to reproduce now (both Ilanit and me can't reproduce),besides,the bug doesn't happen with fixed build according to comment8, move the bug from ON_QA to VERIFIED status.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2019:3071