Maybe I found the cause of the crash of the simulator after the last update. Or at least something related to it.
I tried the older Ortho for the Czechia and it worked. When I compared it with my newer one, I found that there are extra files named *_mask.ttc in the newer ortho. When I tried to put them away, it doesn't seem to crash anymore, neither in flight nor when zooming in the map. So maybe this is it?