I had the session still open, so I narrowed the match-data change to
semantic-mrub-push before it stopped reproducing.

The trace: semantic-change-function
     calls (run-hook-with-args 'semantic-change-functions start end length)
     calls semantic-edits-change-function-handle-changes
     calls (run-hook-with-args 'semantic-edits-new-change-functions o)
     calls semantic-mru-bookmark-change-hook-fcn
     calls semantic-mrub-push

I've forwarded this bug report to cedet-semantic list.