Common Unit Movement Bug?

I've seen some maps with a problem like this, and mine has finally encountered it as well:

Sometimes, a unit will not follow any orders issued to it unless deselected and selected again.

In my map, this only occurs when a unit exits his spellbooks or toggles abilities from 1 spellbook to the other. Could someone explain why this specific bugs happen and/or put it in the sticky of JASS bugs?

If you do a search you ought to find at least a few threads that can provide better information than me, but as far as I know we don't know how to prevent the bug.

However, if you know exactly when it happens you can fix it by immediately removing/adding the unit from/to the player's selection.

Are you using Berserk?

In many abilities' order ID's - but it was there beforehand and it didn't have any problem.