I think I must add this 
This was only my third CTD ever in MSFS.
The first two came after I installed an aircraft Mod from a freeware website.
The third now was this and also it was not really a CTD, just I had the error message and MSFS did not respond anymore and and was not clickable.
The performance in the two hours before that was already very bad, very low FPS.
I don’t know all that much about IT and coding and so on, I think just with the many hours of flight, some data became too much or something deteriorated.
It was just very sad, as I would have liked to get that achievement the way I had planned.
Apart from stuttering and low FPS, the game usually runs stable (meaning it is not crashing) on my side. I stick to only a handful of things in my community folder as I don’t really need many mods. And mostly do short bushflying stints. Maybe that is why.