In the savegame, look at the convoy called "(554) Hibberd Planet Class 4wDM" in the center of view. It has just been set to replace a couple of cars. The moment it hits the depot, the game will crash.
Oh, annoying, the savegame is bigger than 11mb, which is the maximum allowed. How can I give you the savegame?
Perhaps you could send it by e-mail? Thank you for the report.
I found a way to upload the savegame:
A new gitub repository! ;D
So, the link to the savegame is this:
https://github.com/VictorErik/saved-games/raw/master/master/crash_when_narrowgauge_is_sent_to_depot_for_replacement.sve (https://github.com/VictorErik/saved-games/raw/master/master/crash_when_narrowgauge_is_sent_to_depot_for_replacement.sve)
Thank you for the report - I think that I have fixed this one, too; I should be grateful if you could re-test.
This works great too! What a bugsmashing night! ;D