Hey,
thank you for continuing your walkthrough of this, even though it's still in development. It really motivates me!
To address what you mentioned:
I looked into most of your other videos on the missions and I think that Reforged patches (1.32+) definitely affect this in a negative way. For example the Lich heroes have a meager amount of 525 hit points on the March of the Scourge, whereas they should have around 700 or more.
As to the crash specifically: I will play the mission as soon as I can but it should not crash, I've done quite a lot of testing. But remember that this is on patch 1.29.2.
Patch 1.31 should be safer but I think a bug in the game prevents the AI from researching upgrades.
I recommend to get 1.29.2:
Hello everyone, sorry for the inconvenience but I really tried all the means before coming here to disturb the quiet of you. I made the fatal mistake of upgrading my Warcraft 1.29 to 1.30 ... and obviously I regretted it fatally, I ALWAYS use the World Editor but it is broken in this patch, the...
www.hiveworkshop.com
This is from the hive, it is legal as long as you have a legal CD key, at least to my knowledge.
You will most likely lose progress though if you change patches to play the campaign.