Crate BT-25 Noise Gate Issue

[stereomonostereo]

Hey guys
I'm working on a Crate BT-25 bass amp that's having a problem with it's distortion channel. When you play through it, certain notes have a strange decay, like a clipping. This isn't happening on the clean channel. From what i can gather the amp has a built-in noise gate on the distortion channel and i think that's what's acting up with the clipping. However, i can't for the life of me find what is activating the gate on the schematic. Any help is greatly appreciated!

PWA Bass Amplifier PCB Schematics (848SCH_A).pdf

[Enzo]

I'd have to see a noise gate in there before I'd think about what might be activating it. And I don't.

[stereomonostereo]

I'd have to see a noise gate in there before I'd think about what might be activating it. And I don't.

I wasn't seeing one either, but then the manual states "NOTE: The BT25/BT50 employs an internal noise gate to keep residual noise to a minimum".

[g1]

Furthermore, "regardless of which channel is selected, the Clean channel's Level control (#6) must be turned above "0" for the noise gate to trigger".
It is shown on the block diagram: