Since you European passport does not have any stamps from Canadian Immigration in it, and since the ETA for Canada is not mandatory until late September (unless you need a visa for that passport normally), act at check-in like you're a visitor to Canada and you should be able to board your plane without issues, but only if the flights are booked under the European passport. Then when entering Canada, do so with your other passport and the COPR you received at your landing. They might give you a harsh talk at the border, but will let you in nonetheless since you are a PR.
If you did book under your Latin Passport, you will need to reroute your flight to the city closest to the border where you need to go and go via private vehicle, then at the border show your Latin Passport and COPR.
