My zx10r is self-throttling

I don’t know what’s going on here. My 2017 zx10r, 10k miles, all stock except for pipe/moore mafia tune, started rapidly and repeatedly self-throttling when the engine was decelerating with the shift lever pushed in and held in the “downshift” portion of its travel. The shift lever actually needs to be in the “downshifted” position with continued pressure, not just pushed in and out of neutral for this issue to occur. The throttle is completely closed in the video where this happens.

The engine will do this in any condition where the engine is braking with the shift lever fully depressed in the downshift position, not necessarily just immediately after a downshift. For example, opening and closing the throttle again (without releasing pressure from the lever) will cause the engine to do this again without a second downshift.

Self-chopping stops immediately when pressure is released and the switch returns to the rest position.

Attached is a video. I am fairly mechanically minded but I don’t know where to start with something like this. I feel like the clutch is starting to fail, which may or may not be relevant. Any help would be great, thanks!