Hello,
I have the same issue. I have NGX, UT2 AI, Aivlasoft 1.3.2 Sp1 and Ngx sp1c in my setup. I installed fs2crew last weekend and noticed that AI traffic disappear in Aivlasoft DU and DP after a while into the flight. Today I did a test on the EDDM - LFMN route. In the first run I enabled and operated fs2crew and AI traffic dropped to 2 aircrafts after passing TULSI which is the beginning of the route and dropped to none later although there were more than 10 AI aircraft in FSX. Afterwards, I repeated the same flight starting at the same zulu time but disabling fs2crew this time. Well, I am at the initial descend phase to LFMN now and still can see many AI traffic arround. So, I think fs2crew triggers something in this issue.
UPDATE : After writing down this topic, no traffic remained in the DU whereas 17 in FSX. So, there seems no correlation with fs2crew
Just for your information,
Best regards,
Suavi Akar