I have tried all four channels on the remote and still having the intermittent problem. Although, today my wife told me it was quite specific ie couldn't watch/rewind some recorded TV.

How would I use the other remote to test for the interference?

Tonight it really played up. Not working from a distance, even though the light on the extender would flash. When I held the remote next to the extender, it would work most of the time, but not every time.

Gotten to the stage where I've switched the RF off and opened the cupboard doors!!!

Wondering if the extender is faulty.

Thanks