I too am having a shocker of an experience with this "hot potato" of responsibility between VA and QR on these flights.
Booked BNE-DOH-LHR on one PNR, and LHR-DOH-MEL on another, for travel next month. Economy redemptions via Velocity. Specifically picked QR metal for all segments as I travel with firearms in my checked baggage for sporting purposes (competing internationally) and as per their policy VA services to and from Doha do not currently accept firearms.
DOH-MEL leg cancelled (it was the one that continued to CBR). Was rebooked on a whole new itinerary leaving LHR 7 hours earlier than my original service to be able to connect to a recovery flight they've given me... which just so happens to be the VA service that I specifically avoided as they will not accept my firearms.
Not that I'd have known about the schedule change had I not gone to manage the booking last week and noticed 4 segments instead of 2 - shockingly VA and QR both did not send any notification of this to my email or phone. Upon calling VA they confirmed that the schedule change took place two and a half months ago, and also that yes, no notification was sent. They of course told me that it was QR's responsibility (who on a subsequent call later returned serve by telling me that it was VA's responsibility).
Have spent several hours going back and forth between VA and QR call centres and live chats, trying desperately to get either one of them to take some sort of responsibility and assist me, but so far have had zero offers of assistance outside of them rebooking me to something else with reward availability (near zero at this short notice). Their only other solution is to offer me a full refund, again highly unhelpful at this late stage.
I am genuinely not sure what to do next aside from trying the avenues of contacting their executives via email and or LinkedIn, something I never thought I'd have to do (nor do I want to).
I am just fortunate that I happen to have a background in airline operations and ticketing, so I know the systems and what to say moreso than the average punter. God help anyone with no idea regarding these sort of things. It is absolutely disgraceful and it reminds me of why many people detest airlines.