Edge 530 – No temperature or gradient after deep discharge (FW 9.75)

Hi all,
After leaving my Edge 530 unused for ~7 weeks, the battery was fully drained. I recharged it via USB and did a full reset. Since then, both the temperature shows “— —” and the gradient always reads 0%, regardless of terrain. GPS works fine, sensors are enabled, and all data fields are correctly configured.
Firmware version is 9.75.
Has anyone experienced something similar? Could this be a firmware bug or a sensor init failure? Hard to believe both sensors would fail simultaneously after just sitting powered off.

Thanks in advance!