Follow up:
This works fine, so the problem must be in the LED driver receiver it seems:
logInfo("Motion", "hallLights ON")
sendCommand(TradfriP1Bright, 90)
sendCommand(TradfriP2Bright, 90)
Thread::sleep(600)
sendCommand(TradfriP1Temp, 50)
sendCommand(TradfriP2Temp, 50)