You say you're trying to migrate a vdi, where are you trying to migrate it?
To a SR attached to your current host or to another host/pool?
If you're trying to migrate it to another host/pool this is something that i've seen as well when dom0 is not assigned enough RAM, we usually gave them 16Gg which seemed to resolved these kind of issues back when we were running 8.2.0.
I have checked the hosts and they all have non-expired self-signed certificates with:
subject=CN = 10.10.48.152
issuer=CN = 10.10.48.152
matching their IP addresses.