Clunk noise at the Z

Hard to explain but when I pocket out holes I get a clunk, clunk right at the last pass of the outer cut of the hole? It jerks the Z access where the router is like a lot, but only on the last pass or two of the hole. The hole is 1/4” wide.
I have a video with the router and dust collection not running during the carve and everything’s great sounding. The carve is good too. Then at the outer edge last pass it goes clunk clunk?

I have a video Onefinity CNC Users Group (Official) | Facebook