Thanks. I will see what Mike can do first. I don't think it's the roller just the tactile switch underneath it. To change models I have to use my finger nail to gently rotate the roller but it works but it takes a bit longer to change menus/models.

Have manually copied all my models/rates/expo on to the DSX11 although some have custom mixes which I will discover after binding later on.
By chance after visiting your link I spied a virtually new DSX9 MkII with RX and charger and box. Seller wanted £235 at starting point. No chance! No bids so far and one day left. thought about making an offer for it for spare parts. I got my DSX11 with RD921 and three sats via BMFA classifieds for £150 delivered.