I had a big problem but in the end I finally found the problem.
Yesterday, I hooked up my Minilogue to use Zynthian Synth Layers with USB MIDI since I didn’t put any DIN MIDI connectors on my Zynthian.
Each time I played a note on my Minilogue to try a synth layer, the Zynthian kept changing screens and receiving commands to control the UI with MIDI messages. I couldn’t find the solution to disable this. Nothing in the Webconf on the MIDI Options page. Found that there isn’t much either on the Zynthian UI Users Guide - ZynthianWiki. But then I read carefully and saw that These actions are available using MIDI messages on the Master Channel (default 16). In my Webconf → MIDI Options, my Master MIDI channel was on 1. Changed it to 16 and it did the trick. That’s cool 
But I do have a question, if I use all 16 MIDI channels, I will once again have the problem with the MIDI channel 16… which does in fact mean that we can only use 15 channels ?
Xavier