Denon PMA-S10 II input selector shifting by it self?

Hi - I hope that someone in here can helt me :)

My Denon PMAS10II has started to shift inputs by it self - it's not the remote that doing it, and it's not all the time. Most of the time it doesn't have the problem, but then suddenly it starts the shift between the different inputs by it self :(

Do some of you have the schematiks or an idea of what is wrong with my Denon amp? :D

Hope that you can help !