I have two feilds in country-1 with supply roads, a river set to visual only, two road segments set to visual only and all of country-1 HQ\city\strat with auto populated track to each. I ran the mask and the only errors from the error checker are about not having any feilds or HQ for country-2\3.
I was in CM-eye mode watching the trains for the strat auto spawn, then run. When I exited the offline arena the game froze and I had to ctrl-alt-del to task manager. A dmp file was generated. It is attached.
