Mainstage, one patch affects another

[jprykiel]

Hi friends,
I use mainstage on a regular basis, and I think something broke after either switching from Catalina 2 big Sur, or installing last mainstage update.
It's strange and random, but in the process of building a concert, editing one patch can affect another one that I never touched. When I say affect, I mean that the untouched patch will be playing the right plug-in with the wrong sound, or even a different plug-in. These untouched patches are not linked in any way to the ones I edited.
How can you rationalise this?
Do I have to downgrade to Catalina, I hope not.
Thanks for your help,
Cheers,
JPR