bpatcher won't let me change the patcher file

I have made a drum machine step sequencer sort of thing however I noticed one of my bpatches wasn't updating when I edited it's patch. I then went to the inspector to make sure that it's not linked to some older build however, I found that the "Patcher files" option was greyed out and won't let me choose a new file? Any help on this would be amazing thanks :)

Kind Regards,

Drew