I had tried a friend's BOSS dual-footswitch also, and it did not work right. Seemed that either pedal triggered BOTH inputs. I think it has to do with "electrical common", I think that's the term. I used a Volt-Ohm meter and found that one of the connectors is used "in common" for both pedals. I used a different (Studio Logic) dual pedal, for which each pedal is completely independent (no electrical 'common') and that works fine.
So with the Boss, if I had "pedal 1" connected to foot switch input 1 on Genos, and "pedal 2" connected to foot switch input 2 on Genos, when I press pedal 1, it triggered BOTH things (as if I'd pressed 2 pedals).
I liked one of the Boss dual pedals for its compact size, but I just could not get it to work. I was able to get the Studio Logic dual pedal to work OK . . . I had to re-wire it though (not sure of the model number)
Jim