He’s only playing BFD3 on his end. No plugins here on my side. But I finally figured it out. When you create a midi track in a VST connect session it will only connect the output to the “Cue(VST Connect)” so the performer can hear want I play back on the midi track. But in order for the performer to be able to record you need to connect the “VST Connect: Ins…” on the input. Otherwise there is no incoming midi. So if you have these both active it will echo everything back what the performer puts into the track with a second delay or so. So it’s either remove the Cue (output) every time the performer wants to record or switch off midi thru in preferences. I think the last is more convenient because it’s easy to assign a key to do this on the fly.
Forget about this remark. It’s the result of running in circles and not seeing a solution. I mixed up a few things.
Thanks for the heads up!