So, i was correct. They only need to put one try catch, in subroutine that is called for each key press.
And sooner or later it will show it self with detailed description in MSG box.
I'm 99% sure, that is sometimes expecting next letter or previous to be typed, but it isn't there.
Does anyone notice patter if this happens to specific command or randomly?
It also can be helpful if you notice that it crash while typing in middle of word, or if typing new word.
Eg if you type ADIN, and want to add letter C, in middle of word.
Now we just need source code to correct that
EDIT:
I think, for .net application you can actually get line number where error occurred.