DJM 900 NXS2 error 8020

hello,
It has emerged me a problem...
Line input channels 1 and 2 have stopped working and 
also from time to time I get error 8020.
I have already restored to factory value and updated 
the software but there is no way to bring the two 
channels back to life.
I've even tried switching from phono to line and 
the relay switch can be heard perfectly...
Any ideas or solutions apart from changing 
the DWX3713 module?
thank you so much