That would be Forward Collision Warning, as per the manual at Model 3 Owner's Manual | TeslaThings are getting worse, travelling on the motorway facing the sun, I got a red take or taking corrective action. This was without the cruise control or auto steer on. Before that I tried cruise control and it was slowing dow, so I cancelled that.
It has always been based on camera input, hasn't changed since radar was removed. It is possible to have had a false detection, and has multiple settings you can use to tune it down if you need.