Using the AIDA64 Extreme Beta 7.99.7817, the t_sensor reading seems to be stuck at 12 C. HWinfo64 and FanControl are both reading the correct temperature.
Motherboard is an Asus B850i with latest BIOS. Temperature sensor is an EK fitting.
I tried to use stable version that came with the motherboard, but there were a lot of sensors that didn't appear, including t_sensor.
Hopefully this will be an easy fix.