Why does my Garmin Fenix 7 battery drop to 5% after 2 hours on the AT despite Low Power Mode?

I spent three days on the AT (Mile 210‑212) using a Garmin Fenix 7 with Low Power Mode enabled. After about 2 hours of continuous GPS tracking, the battery fell from 100% to 5% and shut down. I followed the recommended settings:

• GPS + GLONASS enabled
• Heart rate sensor off
• Backlight set to auto, timeout 5 seconds
• All notifications disabled
• Power manager set to "UltraTrac"

The same settings on a previous trip (last spring) gave me ~24 hours of runtime. This time the temperature was 45 °F, no extreme cold. I swapped the battery (new OEM) and re‑flashed the firmware to version 15.00.2. Still the same rapid drain.

Has anyone seen this behavior with the Fenix 7 on long hikes? Could a faulty GPS antenna cause excess draw, or is there a hidden setting I’m missing? Any diagnostics steps or firmware tweaks would be appreciated.

• Model: Garmin Fenix 7 Solar, 1.3" display
• Firmware: 15.00.2
• Battery: 1.5 Ah OEM replacement

Thanks.