SKY+ delete button not working. I keep having to buy new (genuine SKY) remote controls for my HD box

[HomeSafes]

This is a strange phenomenon. I have a SKY+ HD box in our bedroom and every few months the delete button on the remote stops working. You press it and the LED on the remote does not illuminate. If I go and get the remote from the living room box I can delete no problem, so it's not the actual box. All the other buttons work just fine. I am on my 3rd (Genuine SKY) remote this year and it's just stopped deleting again! Any advise please, thanks. 

[Annie+UK]

See question Q26 in my Sky Plus F⋅A⋅Q

[HomeSafes]

Thanks Annie, it's not that.
I even stripped one of them down to check for that