Just wanted to mention since I've not seen it explained on this forum, that if you need to do a factory reset, you should disable the automatic restore and set your phone up as a new device. (EVERY time you ever do a factory reset)
Every other forum for android phones stresses this point, but I've not seen it explained here.
Doing a factory reset and choosing the automatic restore does not completely wipe your device and corrupted or broken files from an Android update for example, will still cause problems. All kinds of problems from frequent crashing/rebooting, to enormous battery drain, etc., etc.
If your Axon 7 does not have a hardware problem, a factory reset where you choose to set up your phone as a new device, will take care of it.
I bought my phone after the last update for the Axon 7 was released, meaning I updated the phone right out of the box from Android Marshmallow to the current Android Nougat 7.1.1, and of course I factory reset the phone the proper way by choosing to set it up as a new device, and my Axon 7 works flawlessly. The best and most dependable phone I've ever used.
If you're having problems, try this. See if it doesn't make your phone MUCH better.