Denon DCA 760BL issues

Hi all, I have a Denon 760BL on the bench with odd output issues.

When set to 4ch mode Unbalanced
Channel A input

Output is as follows
Ch A
Left is low distorted,
Right is normal

Ch B
Left is low distorted
Right is normal

When set to 4ch mode Unbalanced
Channel B input

Ch A
Left is normal
Right has no audio

Ch B
Left is high vol distorted
Right is high vol distorted

Turning up input sensitivity on input B causes the amp to trip the relays and it won't turn back on unless the gain is turned down.

I've removed the veritcle boards, cleaned the pots and switches with deoxit and no difference.

The amp idles at around 2 amps
Turning up the gain on input b causes it to draw excessive current then it trips the fuses.

Any help appreciated. Thanks
Hello Perry

I've discovered the issue isn't output level or gain level associated.

I swapped the source unit for another just incase the input signal was bad and no change.

When I use input A and set the amp to 2ch mode bridging the speaker outputs on ch A and ch B causes the amp to trip and shut down, in fact it makes the relays vibrate/buzz they're tripping so fast.
My bench supply is 13.8v 30 amp has no trouble powering most amps

I don't know how to test the speaker voltage when it shuts down, I tested with meter set to DC and it read open circuit when the amp shut down.

When driving one channel it will play at low volume it goes higher if I turn it up thennit cuts out.

The audio has a distinct echo on channel A right spk and a strange bass tone on channel B right speaker