https://github.com/kubernetes/kubernetes/pull/74840 fixed a problem in kube-proxy where if certain TCP ACKs got lost (eg because there's a lot of traffic and so some packets are getting dropped) then the connection might be spuriously closed when kube-proxy received an unexpected retransmit. There's not an easy way to test this but it's a simple patch, and it appears to have fixed the problem for the original filers, and the fix went into kube 1.15 and hasn't caused problems for anyone else, and now we have a customer who would like it backported.
Weird. I'd swear I set this to Version: 3.11.0, Target Release 4.3.0, but somehow it ended up with Version: 3.9.0, Target Release 4.2.z.
This is already fixed in 4.3, and there is no useful QE that can be done (other than verifying that it didn't break anything else, which has implicitly already happened since the fix has always been in 4.3).
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-2020:0062