I think it has to get pretty hot before it clips. The only time it has been obvious for me was when the controller was exposed to the sun and dropped from over 12a to under 6a quickly. I do know it would have shut down had I left it there.
I'll has to see if I can get the controller to warm up in the shade by pushing 16+ amps for a few hours and then see if cooling it has a affect. Not as hot as it got in the sun but still pretty warm. I'll keep track of the temps so that if it is changed, I'll know how hot it has to get before any clipping happens. I suspect it wont happen unless I don't allow the back side to get ventilation. I've seen 15-17a for hours at a time and haven't had it overheat yet.
BTW no response yet but it is the weekend, even in China.