Correct Key signature in imported xml file

Hi. Hope someone can help.

I've imported a four part sax score as and xml file.

Musescore has assigned concert G to the whole score and chosen the instrument as piano

All the notes on the score are correct and correspond to the original pdf, however the Tenor and Soprano parts have a key signature of G instead of C. It's probably the fault of the program that exported it, Playscore for Windows, but there is no way to correct that.

I'd like to just get an eraser and rub out the key signature and everything would be perfect becasuse all the accidentals are notated correctly but when I muck around with changing instruments or key signatures the whole score gets messed up.

I'm hoping there is a way to correct this in Musescore, but if not, would it be possible to correct this by editing the actual xml file before importing it? I've looked at the file in Edge but I wouldn't know where to begin

But I could be barking up the wrong tree. Maybe there is a whole different way to approach this

Any suggestions on how this could be quickly fixed?