Having the same problem with my GG case being cracked near the power button & because the case isn't flush with the phone most of the time I hit the home button I'm taking screenshots or I'm getting the shutdown menu. Also had issues when going into recovery & the power button choosing a menu for me. I'm gonna contact GG about a new case. FWIW, after the battery died Friday afternoon I only charged it once since (Friday night when I got home) but that was because I was stuck in the house all weekend due to the storm so I didn't use the phone.
Shoot me a PM and I'll see that a new back plate gets sent out to you.
link at bottom.