Completed the trip.
Although the bag was through checked LAX-YYZ-YQB, the WS agent confirmed that the bag would be automatically transferred but "suggested" to wait and see if the bag would come off the belt. 3 hours' connection time so decided to hang around.
The bag indeed came out. I picked it up and went upstairs to re-check in.
Who runs this airline? So amateurish.
Thanks to the WS agent who obviously had seen enough of these mishaps to give the correct advice.