Code 61 OUT -> Kenton Merge 4 IN
MS-101 OUT -> Kenton Merge 4 IN
Volca Samle OUT -> Kenton Merge 4 IN
unplugged:
Some Yamaha OUT -> Kenton Merge 4 IN
Drumbrute Impact OUT -> Kenton Merge 4 IN
Kenton Merge 4 OUT -> Pyramid IN
Pyramid OUT A -> ESI M8U IN (MIDI THRU 1x15)
ESI M8U OUT1 -> Volca Sample IN (Ch. 1-7)
ESI M8U OUT2 -> Some Yamaha IN (Ch. 8-10)
ESI M8U OUT3 -> Monologue IN (Ch.11)
ESI M8U OUT4 -> Volca FM IN (Ch.12)
ESI M8U OUT5 -> Volca Keys IN (Ch.13)
ESI M8U OUT6 -> Volca Kick IN (Ch.14)
ESI M8U OUT7 -> MS-101 IN (Ch.15)
ESI M8U OUT6 -> Drumbrute Impact IN (Ch.16)
The modded Volca Sample is the clock source. The Pyramid is set to Omni Multitrack BKA, MIDI Echo: Auto MIDI A, consistently sending clock to MIDI OUT A. I am able to control all instruments from the Code61 and the Pyramid is recording input from the MS-101 aswell as the Yamaha and the Drummachine (if connected). The Monologue triggers the MS-101 @ 1PPQ. The MS-101’s Clock OUT is disabled.
Things are literally working as intended but i am getting nasty stuck notes to random instruments, in random intervals at random points of a performance. This could be 1-5 minutes into a song or take aswell like 30 before it starts happening. No action (any change of encoder, potis, keypress) is required to make this happen and it also doesn’t seem to matter how many Tracks are active. For instance, I could just sit next to the gear doing noting but watch TR1 loop nicely and at some point everything is ruined. Double tapping the STOP button stops the hanging note but along with it all the rest aswell which is of course the total killer for any kind of performing live. The Volca Kick even needs to be rebooted at times if the beating got harsh 
So as I typed this, the same 4 bar sequence ran flawlessly through the MS-101 for an hour now while directly being conncted to the MIDI OUT A of the Pyramid (the port that usually goes into the Input of the Midi Interface (M8U) instead). I think it is more or less save to exclude the Pyramid from being the cause of the problem.
Any ideas are appreciated, please tell me i am just missing / overseeing the obvious. TIA!
Edit: apologies for the FAT text. I tried my best to revert it without success