Part of the tool deletion process runs on the sgecron server (currently tools-sgecron-2). It uses the tool's own credentials to dump and then delete any databases owned by that tool.
Right now I'm seeing this fail with
Access denied for user 's55337'@'172.16.4.1
This could be a result of the database migration or a new issue with maintain-dbusers but I'm guessing it's the former.