this rings a bell, I’m sure i fixed this problem at some stage…for now i can only give you this link for idea’s…
this could also be systemd trying to resolve stuff, there is a bit of a bit of battle going on between the systemd resolver, and normal dns resolutions libraries on the machine.
like i said, just idea’s…
are you containers restarting at any time? could be systemd start up ordering within the container…something to watch for.