My usual M.O. is to complain to everyone. On top of CATSA, you can also let your MP and/or Minister of Transport know and the airport. I would preface the complaint to the airport by saying that you understand the airport is not directly responsible and have already contacted CATSA directly, but CATSA experiences reflect on the airport overall and I'm sure the airport and CATSA have a good working relationship to resolve issues.

I never expect an actionable reply, but I figure the squeaky wheel gets the grease. No complaints = everything is fine.