I know why: the image used. All images used in events must be 24 bits deep. The image obrona_narodowa.bmp is 32 bits deep. There are 3 images with this problem (the others are 'olympics' and 'slovenia'). The image 'gibraltar' has a wrong size too, but that doesn't create CTD.
Anyway, replace the offenders with
this and the CTD should stop happening. The folder is gfx/event_pics
However, there are other things that will cause a CTD, sooner or later.
For instance, event 3001014 (in ai_eng.txt) tries to call for the inexistent file ENG_Build_Land.ai from the switch folder.
Same issue with event 3006013 (ai_ita.txt) and 'switch/ITA_Naval_WestMed.ai'; event 3049005 (ai_u05.txt) and 'switch/USSA_Dday.ai'; event 3999002 (ai_research.txt) and 'switch/Minor_NoIgnore.ai'.
Other issues:
Event 1350003 (in Mobilization_events.txt) has JAP duplicated in the TAG section.
There are 37 mentions of rocket-artillery in the scenario files of 1914, and 2 in the 1936 soviet scenario file (ids 206 and 243). This brigade is not defined.
2 Japanese divisions have incorrectly defined brigades (ids 115 and 229).
There are 18 mentions of the not-defined brigade 'naval_torpedoes_l' in the 1936 scenario files. On of them is in the JAP file, the others in the USA file.
The china scenario file (1936) mentions an anti_tank brigade, that isn't defined.
There are also some invalid targets to several IA files, but that's a minor concern.