So I did the update to 7.0 and had a bit of a scare where one of the drives wasn't detected, but a full power cycle fixed that. So I was able to get it up and running. I then went ahead and invoked the mover and it reduced the cache usage quite a bit, but it's still hovering about 60 GB more than it was when it was fully moved over prior to the 7.0 upgrade. So I looked through the cache drive with the built-in file explorer, trying to find something that might have taken up this room, but I can't find anything new that's large. It's very weird. Is there something I'm not thinking of? Can anyone maybe do an idiot check on me? I'm kind of stuck.

Used QDirStat to explore further and I'm still stumped lol

You are likely to get better informed feedback if you attach your system’s diagnostics zip file to your next post in this thread. It is always a good idea when asking questions to supply your diagnostics so we can see details of your system, how you have things configured, and the current syslog.

So despite invoking mover several times yesterday, overnight it cleared up and the mystery file is gone. It never showed up in QDirStat, it showed about 180GB and Unraid showed 260GB being used... I guess we'll never know.