It is weird how issues seem to interact with each other. I had switched to Navigraph NavData, before problems began. Furthermore I had installed another airport (LFOO) from the market place. Subsequently ATC just stopped working. On top of that a different marketplace airport (LFOU) started to cause CTDs. So I removed everything from the sim to isolate the problem. At some point, ATC started working again. Navigraph on its own seems to work fine. LFOO on its own also works fine. LFOU still CTDs, don’t know when or how that started. Next I’ll try combing LFOO/LFOU and Navigraph NavData. Let’s see what happens.
Crazy, all I want is to have a little fun with the sim, I could do without debugging.