Marker Duplication to Infinity and Beyond

I have a multicam sequence with two cameras. When I add a marker in that sequence (by pressing control+m), in a little while that marker gets duplicated in the Markers panel. If I scroll down in that panel, it duplicates again. This process continues indefinitely until the Markers panel has hundreds of entries. In the attached screen shot, there are exactly two "real" markers in the sequence; the rest are auto-generated clones. I worry that this bug is going to corrupt the sequence, so I have stopped using markers altogether and am just manually writing down timecodes, which is pretty sad.

Premiere Pro 15.0.0 build 41, Windows 10 Pro