Chain grinds and makes horrible noise with decel braking only?

Mini Bike & Go-Kart Parts

So my spring loaded tensioner bounces like crazy on decel braking and makes a horrible noise. Almost sounds like it's locking up or binding. Tensioner maxes out travel. Is this a symptom of improperly aligned gears possibly? Only happens when braking.

Built 4-5 of these now and this is the first I've had any issues with this. Wouldn't normally care but I only have a rear brake on this setup. No troubles unless I apply brake. Other wise it's nice and smooth. Doesn't throw the chain ever.

Haven't had time to really dig into it yet, figured I'd ask here first and see if it was a common issue w a common fix. I was thinking maybe a fixed tensioner would cure this? Get rid of the spring?

I've had a similar problem with one of my bikes, it's like the clutch was staying engaged when decelerating/braking. If you still have one of the other bikes that you have done this to, try swapping the clutch from the one that works to the one that has the issue.