Rebooting domoticz seems to solve the problem. Switches responding as should now. Running Domoticz version 3.4834 on a Pi2.

Also have the same problem. I have made some dummy switches, so these can't disappear. I created a blocky, when switch-1=on or switch-2=on then set switch-3=on. Also created another blocky, switch-1=off and switch-2=off then set switch-3=off. For some reason i get this error in the log: Error ...