I'm running into this issue after upgrading as well. I tried updating the mysql package to the latest version from the main repos to no avail. I also ran into the issue w/ a Clickhouse server I have in an LXC container (it couldn't calculate its available disk space because of a permission...
Sorry to resurrect an old thread, but for those landing here from a search engine: in modern versions of Proxmox you can go to Datacenter > Options > Bandwidth Limits > Migrations to set a max transfer speed for migrations.