We can't really do much as the game does not crash every time a unit attacks the ai.
I highly doubt that this is a bug with the game, more like bug with your code.
Do you have any code that runs on a unit attack ? DDS ? or "Unit - A unit is attacked" event? or "Unit U receives damage" even ?
On the other hand, is that on the PTR ?
If it is some sort of a bug with the game, best would be to describe very well what is happening and sent to blizzard.
If it is easily reproduce-able even better. Now again.
And now again, I highly doubt that it is a bug with PTR, more likely to be a problem between your code interacting with something new.
Show us some code, what have you done wrong ?
regards
-Ned