Strange battery draining issue

Hi,

I know there are several threads dealing within battery problems, but I did not find a similar issue. 
I own my fenix 5 (latest update) since march this year and I was always happy with it - especially since I never had any issues with battery life.
The problems started a few days ago, when I installed and ran a HRV app. After doing so I went to bed, then waking up in the middle of the night recognising, that the battery was fully depleted (charge was 93% prior to this). I recharged, but the watch was maintaining a discharge rate of ~1%/min, which I consider really high, the watch was even getting warm.
The draining stopped, when I deinstalled the HRV app. So I was happy having solved the problem.
That evening I went for a run of approx. 1 hour. After that the watch lost 40% of its charge. 
I then deinstalled all watch faces etc. and did a soft reset, which solved the issues again. 
However, I was experiencing several other draining incidents the last few days, mainly occurring over night.
I decided to do a factory reset, but wanted to backup my data first, so I connected to GE. Then the latest firmware was installed, and I wanted to give it another try before resetting the watch.
To my pleasure the draining did not recur. Yesterday evening I installed a watch face, which I were using since I had the watch (no issues regarding draining), but over night I ended up again with a depleted watch. 
The draining could be stopped just (and only) by connecting to GE and synching the watch. 
Does anyone else have a similar problem? 
Additionally:
- When I do not charge the watch to 100%, percentage is creeping up with +4-5% the following hours
-I have installed the new connect iq app beside the garmin connect app
Something seems to mess up the watch and it only calms down after connecting to GE.
Regards