I got the usual instrument pickup softlock, but this time around I cannot retry picking it up since the boss of Eagle Tower is defeated and the door of the instrument room is locked.

I've given myself the instrument through altering the savefile but the rooster is still following me and Marin isn't where she's supposed to be, so I cannot progress. Any idea on how I can edit the savefile to maybe reset the boss or move forward the set of events?
Thanks

Ok, I solved it myself. 
If you have this same problem, find the next line in save Game0:

s d7_enter_I 1
and make it:
s d7_enter_I 0

This will make the door stand open