Dab tuner freezing

I would appreciate any advice and possible solution to remedy the problem of my Dab tuner freezing. A few weeks ago I purchased a CD/Dab tuner seperates from Currys. No matter how I tried the tuner would not scan any Dab radio stations, this despite erecting an external aerial. Currys were happy to return my money which I appreciated. I have since bought a different make of Dab/CD player and the Dab stations loaded without any problems whatsoever. The sound quality is ideal, but I have a problem with the tuner freezing when I am listening to any of the radio stations. The music still plays but I can`t change stations or switch to FM or to CD player - it just freezes everything. To remedy the problem I either disconnect the lead from the rear of the unit or switch off at the wall and start all over again. This will happen four or five times an evening and so as you can imagine spoils my evening`s entertainment. The unit is a Denon DRA-F107DAB. Grateful for any help. Bob