Thanks, appreciate it.

Not sure what circa 20k vs 21k means. Did a quick google search and couldn't find anything, maybe some experts here can weigh in.

YYC009 may have booked as one-way, however I don't believe that should matter as I have been able to book few return itineraries.

Aeroplan changed systems and agents are now more restricted to book multi segment itineraries. Having said this, I booked one 10 segment trip last year for travel earlier this year, which I had to cancel due to COVID-19. Also booked three multi-city roundtrips last week and they all included EWR-SIN-EWR segments. MPM that agent gave reluctantly gave me, matched what I showed. All three bookings were slightly below MPM (however borderline). On one itinerary, agent couldn't see availability on SIN-EWR segment, even though Aeroplan website showed available. I booked that segment separately on website at 77,500 miles while agent was still on phone, gave him PNR and he worked with ticketing folks to include that segment and also refunded 77,500 back to my account.

If you do call back, maybe insist with agent that trip should be within MPM (YYC-CMB MPM noted earlier in thread). Once agent is aligned that routing is valid, then you can go through confirming availability for each segment. If there is one segment that agent does not see but you are able to book separately on Aeroplan's website, let agent know you can book and give her separate PNR he/she can work with ticketing to merge as well as refund that separate segment miles back in your account.

I know it's a pain and fact you'll spend more time on phone, but could be worthwhile if successful. Good luck and keep us posted.