The latest 2024.12.2 release brought in side-effects for rest: functionality. When setting values it flips to unknown, then to the new value. It did not do this on 2024.12.1. My timeout was set to 1s, and raising this to 5s seems to solve the problem.
Has there been a behaviour change where a 'timeout' sends the sensor to unknown - whereas previous releases did not do this (?)