Switching fader page kills Submaster

Hej there,

I'm in new theatre, not knowing all the details for setup, but what I know is:

2 Gios, via LAN and an unmanaged switch connected, one primary, one secondary, the primary one with unmotorized 2x 10 faderwing.

When switching between faderpages, a submaster (working light) is put down invisible background, without moving it by hand. This problem doesn't happen all the time and also with different operators and different showfiles. All shows in this Theatre are made from one basic showfile. All settings from the submasters are the same, but only one special submaster has the problem. 

does somebody have an idea, what the problem could provoke?

thanks in advance, Dominik

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