Phone randomly shuts down and loses all battery

I own a Samsung Galaxy S Advance I9070 and i've got a problem with it. for the past 3 weeks, it randomly shuts down, and drains all it's battery, and won't start until i plug the charger in it, after that, the battery goes up instantly to somewhere between 70%-100%, and then i can open it without any problems, then. it works for a couple of mins and it happens again. I even did a factory reset but the problem persists .

Calendar storage loses its data

Nexus 5, rooted stock 5.1.1, xposed.
For privacy reasons I do not sync with Google and use a firewall.

Problem:
Every couple of weeks, the calendar I use suddenly goes blank. The problem is always that "Calendar Storage" has lost its data. If I use Titanium Backup to restore the most recent backup of Calendar Storage, I get my calendar data back. But because of the way tibu works that is sometimes 3 days old.

How can I figure out what is erasing the data in Calendar Storage and fix the problem?

Thank you.

watch loses phone pairing every 5 minutes

I've had the Huawei for about 7 months now, and it has been absolutely rock solid on it's bluetooth connection to the phone. The last 2 or 3 days it has been losing connection and requesting to pair again about 10 times an hour which is rendering it unusable.

I've tried a factory reset on the watch, but it doesn't seem to resolve the problem. I'm running stock AW 1.5.0.2954763 and stock Android 6.0.1 on my Xperia Z5. Tried googling around but no-one seems to have the same problem. If anyone can suggest a fix I would be most grateful as I love my Huawei! Next move is to try a factory reset on phone and watch together and see if that works I guess but I'm reluctant as it means setting up banking apps yet again (the bank thinks I've had 5 new phones in the last 3 months!!!)

thanks :)