2 HTC phones overheating running same waypoint mission

I just bought Litchi a week ago. A strange thing happened today as I was running my 1st Litchi waypoint mission to test it with my old Mavic Pro. On the first test, my HTC U11 phone overheated dramatically, so I shut it down and switched to my older phone, an HTC One X10 and ran the mission again. It was a short mission, only about 5 minutes in all. But the old phone overheated as well!

The mission ran correctly, and there were no error messages - nothing. Yet both phones overheated running a short 5 minutes waypoint mission! Both phones run DJI GO4 fine - without any overheating at all.

Does anyone have an idea about this - what might cause both phones to overheat so quickly?

Your phone can be turned off altogether when performing a mission on the mavic pro. However, your problem has not been discussed before. You may have enabled location services on your phone.

Yes, I have enabled location services on both phones - why is that a problem?

The problem is not location. Problem with google location function

Can you tell me more?