Reaper DAW - 3 instances - 3 midi channels - unstable

In Reaper I put Midi Guitar 2 on 3 tracks.
Under interface (MG2) I set input channel on track 1 to 7, track 2 to 8 and track 3 to 9.I use FCB1010 to send Program Change and choose patches. But the input channels are not stable, after some use or time they ‘like’ to have the same channel. I know its one plugin, but is it possible to lock the input channel.? I have tried to disable the instances, mute the tracks but I cant stop then to change.