let me add some ideas:
- enable mDisplay -> Tools -> Settings -> Check "Ignore Camclock status"
- disable mDisplay -> Tools -> Settings -> Check "Use GenICam Camera parameter"
- start the acquisition in microDisplay FIRST
- after start the acquisition of the three cameras in GenICam explorer
- last start the trigger
If your process has multiple DMA ensure that all DMAs are started.
I hope that one of these ideas help you. Basically your explanations are all correct and we have bring this to work in microDisplay before. In an SDK application it is no problem anyway as the cameras are started manually anyway.