touchable control surface stops responding

I am using server version 1.749 on Win 10 Pro, Version 10.0.19042 Build 19042. Ableton Live 11.0.12. All firewall ports are open and I have Bonjour and iTunes installed. Using the Android app v. 1.727. Everything seems to be set up correctly. After starting Live and the app, I get a connection for a few seconds, but then the control surface stops responding. I have tested this very often with different Android devices and different network connections, but the problem persists. Restarting the server somethimes restores the connection, but looses it quickly again.
I am testing touchAble Pro every now and then for a year now, because I really want this app to work, but again and again it is so buggy and laggy that I end up not using it anymore. I really hope you guys can fix these issues soon!
BR, Yannis