It wasn't checked if there is a cluster with matching architecture for imported VMs.
There was no cluster in Cluster dropbox on second page of Import VM dialog when VM selected for import had architecture for which there was no corresponding Cluster in selected Data Center
* Split table allowing to select VMs for import shows architecture, format: "vm_name (arch)"
* Selection of VMs is validated:
* The selection may only contain VMs of one architecture
* The selection may only contain VMs of architecture that has at least one architecture corresponding Cluster in selected Data Center