I had some problems when I first started using PL (here) which I never got to the bottom of. What camera are you using and is all the metadata written directly into the XMP file or is something changing the RAW? With my Leica CL it is the latter, an XMP isn’t even created - you could check the file hash to confirm.
I made the mistake of changing multiple things at once, which seems to solve the issue though I have no real idea which change worked.