Hi miki! I've just tried to reproduce the crash in an internal version of DCS with a fellow tester, but it didn't crash.
What I did was:
Join as gunner.
Successfully shoot a truck with ATGM.
"Escape" > "Select role" > "Release slot"
Neither me, the other tester, nor the server crashed.
If you keep having the crash after the next DCS update, please ping me here.