Ok, I'm once again having some really odd issues.
SnapRAID is telling me to fix some issue by running snapraid -e fix, which comes up with an input/output error.
I try to delete the file in question, as it's only one file, which locks the drive and puts it a read-only file system mode.
WTAF is going on here?
Using the commands here OMV is suddenly read only unlocks the drive again, but I can't fix the problem, as it goes in a loop like this.