ur44 line 1 and 2 Problem


I own a ur44 since 3 years now and only used with condenser mics.
I recently tried to plug my guitar directly in and channel 1 and 2 are unusuable. low/no gain, crackling sound and lot of hiss when I raise gain.
No effects activated (as I can see), tried different psu, tried disconnect the unit from my pc and monitor. Nothing worked so far.
The hiss is present also when no instrument attached and unit not connected (just monitoring)

Is this an hardware problem or I am not seeing something? (with mic they work fine!)