Dimming actuator channels still live though channel is switched off

Phase dimming actuators such as Theben DM 8-2T (230V universal actuators) always (regardless of manufacturer or technology) have voltage on the output when a channel is "OFF".

Always disconnect the fuse or isolator of the incoming circuit from the supply before working on connected loads.

For example see section 2.1 in this Theben manual for safe operation, and also 5.4.1

Possible solutions to the problem are:

1. Set load type to LED in actuator ETS parameters.
2. check that the load is greater than listed minimum load in data sheet (eg. Theben DM8-2T minimum load per channel is 2W)
3. make sure the driver/retrofit LED is dimmable.
4. Send details of driver/LED to manufacturer's support - they may suggest a reserved setting in parameters, or use of an RC Filter. 

If 2,3,4 are Not possible the change to a relay channel or try another driver/LED.