B&K Reference 7250 Trouble/Help

I am wondering if anyone can help me out, i recently purchased a used B&K Reference Series II amp and when i hooked everything up i noticed that the front left speaker was cutting in and out/static and mid/high volume. So i moved the FL speaker to another channel on the amp and boom works perfect. Tested all other channels and works perfect except for 1 of the inputs. Tried swaping the speaker fuses on the back but still same issue, and i have all the volumes set to max but its just the 1 channel that messed up. I haven't contacted the manufacturer cause there closed ATM.

Any ideas what it can be? Is it something that can be fixed or repaired or am I just stuck with a 4 channel amp?

Any help or suggestions would be greatly appreacited.