As reported at [X] Mapping failure on ALBUMARTIST and confirmed, in V2.45a (beta) adding a mapping rule for one placeholder can break another placeholder, and hence break format strings, custom columns and scripts. This happens every time two placeholders are mapped to the same field.
I think this is a serious problem. I have dozens of scripts which I cannot afford to have break because I add a mapping rule. I want to create scrtips that reply on a mapping rules (hopefully solving the long-outstanding and pressing MP3 /FLAC album artist issue) but I cannot safely give such a scipt to another user and ask them to add the mapping riule while that will break any existing script using MP3 or FLAC album artist.
PLEASE could this be remedied before production release. What mapping should do is allow any placeholder to take the value from a given metadata fields WITHOUT interfering with any other placeholder doing the same. This surely cannot be hard to code.