[Closed] Non-U-Turn Revelation Knocking on Rebound

I have a rev (well, a bastard, it used to be a alu steerer'd sektor until I put the blackbox moco and rebound assbly from a rev team in it and new stickers on it), running at 140mm. Solo air. I'm not getting 100% travel, but I assume I have a little bit of a hydraulic lock in there and it's only by like 5mm, so i suspect it just needs an oil change and re-measuring.

ANYWAY

It's developed a quietish but noticable "knock" like someone inside the fork is tapping with a tiny rubber mallet on the stanchion at almost exactly 50% of the way through the rebound cycle. It does this with 100psi as much as it does with about 10.

Any thoughts?