I tried to run your example in the latest version, but it is missing your "mydefs.h". Also I don't know what your constraints are, what the scheduling options are, etc.
In any case, the best bet is to try the latest version, and try the default scheduling options. We just released 12.2 last week. Whether it's an issue with your design or not, we consider any crash to be a bug. So if this issue still persists in 12.2, please file a bug report with customer support (http://support.cadence.com)