So add this to the list of AVD being a huge PITA lately between the failed RDBootloader/AVD Agent upgrades and random AVD Agent kicking people off this happend today.
User was on a bum host, logged user off through Nerdio.
User reconnected to another host and received the Container in use Fslogix error.
I used Pshell to connect to the tenant, connect to the storage account, locate the user's SID and then run the close command to detach his container. Yesterday it was 26.1 GB today it is 2.25 and he's lost all his customizations.