Battery Drain & Pace unstable

I recently bought a Forerunner 965 last Saturday to replace my Fenix 6 Sapphire after 2 years of use. Currently, I'm facing two issues:

  • Rapid battery drain: When I bought it on Saturday, the battery was at 60%. Yesterday, on Monday, I charged it again. After fully charging it, the battery drains very quickly. It seems to drop by 10% in about 4 hours (with the screen brightness at the lowest setting, no phone connection, no Wi-Fi connection, only the Auto Display mode On).

  • Pace fluctuation: I usually run at a steady pace of 6 minutes per kilometer, but today, during my second run with the Garmin 965, by the 7th kilometer, the pace was showing as 3 minutes per kilometer. I was very surprised because my running speed was consistent (6 minutes per kilometer).

Software version: 18.26

I've used the Garmin 245 and Fenix 6 before and found the pace and battery to be very stable. I didn't expect the Garmin 965 to have such silly issues. Indeed, it feels like a waste of money buying this 965 model.