Venu 3 suddenly slow & high battery drain on 14.15

Hi everyone - got a new Venu 3 a few weeks ago, and have been very happy until a few days ago. My problems might have started (or I have become aware of them) when I started experiencing the apparently known boot loop bug. Ever since resetting the watch, I have experienced the watch being quite slow and laggy and in top of that having very high battery drain outside of activities. I have tired to turn the watch on and off, reset it, load an older software version, load the beta version - nothing helped.

I have also noticed other bugs - eg the weather app not updating location, the watch resetting itself on its own once, the booting logo sometimes appearing while the watch is on. 

But in general it's the lag that drives me nuts, and the battery drain is very annoying too. I don't want to send it back if I can avoid it, so any help would be appreciated!

Thanks a lot!