We booked travel to Scotland using points from our Chase Sapphire Reserve in the United portal and paid the overage and taxes via the credit card. The itinerary was not ideal but it match our travel dates and included business class on the flight to Scotland. Itinerary below for clarity.

Outbound
Cle-yyz (air Canada)
yyz-dub (aer lingus)
dub-gla (aer lingus)

return
gla-dub (aer lingus)
dub jfk (aer lingus) paid upgrade for legroom
ewr-cle (United)

The night we were to leave Air Canada cancelled their leg. We called United and they took control of the booking as air Canada had planned to rebook us 3 days later through them. Unite routed us through Chicago on an early morning flight to Toronto with a 9 hour layover for the aer lingus flight. They had to overwrite our original registration to do this we were told, but we still had the same confirmation number.We were given paper boarding passes.No biggie. When we got Toronto we realized that we had been downgraded from business to economy. After many hours on the phone we thought we had that straightened out and were told to go to the aer lingus desk for new boarding passes.

When we go there we were told that the boarding passes that United generated in Cleveland were not authentic and that not only my wife did not have a seat in economy or business. Both aer lingus and United could see the reservation but could not assign a seat. After 2 more hours and the aer lingus desk getting ready to close we were told the only course was to purchase a one way economy ticket from Toronto to Glasgow for my wife at a an expense that was higher that the round trip would have cost when booked. We did with no other choice.

Oddly, my wife was lead passenger on the booking and my ticket was not impacted at all.

we had a host of other travel issues with aer lingus during the journey that included lost luggage, delayed flights and cancelled flights, downgraded seats and downgraded.

I am not sure if I have any recourse with United. The agent on the phone had said they would reimburse for the flight we paid for but I have no proof of this. This does seem to fit there refund form request.

Guidance would be much appreciated.