If the team leader commands the AI to go behind a cover (wall, bush exc), if after will command to change stance, the AI will never do this forcing the commander to move it away, ask to change stance and then go back to cover.
This bug is here from so many patches, guess it should be solved once for all :)
1-Open editor
2-Create player teamleader and at least one friendly AI soldier
3-Play and give AI order to take cover behind an object
4-After the AI takes cover, ask to change stance and they will never do this
5-Move AI away from cover, then ask to change stance, it will work
About step 4 I'm not sure if AI won't change stance also if the player will ask it to do so after he already ordered AI to take cover.
You can easily try this within the editor, anyway.
I'm not 100% sure if this bug is there with ALL the covers or only with the majority of them.