Impossible to select Custom MIDI Style for Drums track

I can change MIDI Style for all the other tracks (Piano, Guitar, Bass, Melody ....), but every time I change MIDI Drums, the new Style chosen is displayed (Ex : Custom MIDI Style : 1 Standard Drum Kit (pnosimp4.STY), but when I play, I hear the old Drums Style, so no change.

I opened several projects, Biab templates which I didn't touch, but it looks like the Drums track is locked and I can't change it.