@Bhowe 

Heat could be an issue if the temp in your garage gets too hot.  If you get a small fan like the type you could clip to a shelf or a desk, and blow air directly accross your router's air vents to help diisipate heat, that may help.  Otherwise, it could just be a symptom of your router on the verge of total failure.  Otherwise, check to see if there is an updated firmware you can flash.  If so, once updated, factory reset one more time, set things up, and see how it goes.  I could not find any reference to the firmware version you provided, so it looks like there are updates available with the most recent being Archer C3200(US)_V1_170707.

Good luck.