As for what I'm moving, it's anything between folders. So if I want to move a download from my downloads to its MergerFS home on a local mount, I get permission denied. If I use Krusader to try to move the files between downloads and , I get a permission denied. If I try to modify content on my laptop via file sharing, I get permission denied.
This is all I get in Sonarr:
Access to the path "<file>" is denied.
EDIT: This issue is resolved (for the time being) because of the fixes here.