Why is my battery depleting so quickly?

I recently fixed my htc one m9 LCD after dropping it. It wasn't that big of a fall, however it damaged the LCD without cracking the glass. So I went ahead and fixed it. I have to mention I am trained and have repaired htc models before so I have a good idea about what not to do when it comes to repairs. After the job, for some reason my battery has started dieing really quickly. It doesnt last more than 8 hours standby.

I haven't had the issue prior to the fall/repair so i went ahead and changed the battery because maybe I damaged it. However, despite my efforts, I am still facing the same issue. The only improvement that I've had is that it's not heating up as bad as it use to.

In addition, it randomly activates airplane mode.

Please help !