I had to uninstall Garmin Connect, not even that SP accu drained 15% in 50mins in Standby the Phone was getting really hot.
After deinstalled Garmin Connect my S7 cooled down and accu usage is back to normal.
I reinstalled Garmin Connect, and its back to normal accu use, now from other apps it shows 1% used for Garmin Connect.
Dont know what caused Garmin Connect to use so much accu and heat up the phone, but a solution is to deinstall Garmin Connect and reinstall it.
I maybe found the problem. Garmin Connect was hanging while syncing with 5x. So please take a look at sync, as its really dangerous if the phone gets so hot.
This is happening to me aswell (Beta FW 4.14). The GC app gets stuck on syncing (trying to send some "software update") and starts to drain the battery insanely fast.