Trouble with triggers and insert .. on duplicate key update
This question came back on my radar after a recent comment was posted. 

This issue at the time turned out to be this reporting table that was meant to be maintained by triggers was on a slave only.

The insert on duplicate key statements were getting flagged as not safe for statement based replication and getting pushed through in RBR (the stream was in mixed mode).

RBR events do not fire triggers.