odd crash

Just curious, what does footman have or not have that other units don't have or have? Because on my map, when I add ability to any other unit through triggers, it works fine, when I do the same to the unit based on footman the game crashes violently giving "FATAL ERROR!" about referring to a memory location that could not be read. I tried modifying the stats to match the stats of other units, and tried resetting them to default, it crashes all the time. The weird part is when I give him the ability of hp bonus based on hp boost item and modified to be a unit ability, the game doesn't crash. All the abilities that I tried that cause the crash are based on Neutral Hostile abilities if it matters. When the footman is given the same abilities through object editor, it works fine without crash, when it's done in-game through a trigger, it crashes. Like I already said no other unit crashes, so I find this very weird. There is an easy way around, I can base my unit on another unit instead of footman, but I'm just curious if anyone knows what might be causing this.