Because I'm a sucker for punishment, I was trying to book another award flight with QR and ran into a blank screen on the app when trying to pay (both by Apple Pay and selecting other payment types).

The awards flights disappeared and weren't available for booking for a while, but reappeared so I tried to book again, this time via the website and paying via Paypal. This time I received a message saying "need form of payment" but no option to click anywhere else. I received an email from Paypal saying payment was authorised and I could see a PNR in Manage My Booking, but no e-ticket number or email, and no Avios deducted.

The agent reversed the payment (still shows as a pending transaction on my bank app), and advised that the issue was because I didn't have the full amount of Avios in my Privilege Club account and it was failing to pull them from my BA account despite them being linked. He suggested transferring the full amount of Avios first and then making the booking.

I did that (though initially received a "swift avex transfer amount is invalid" error) and successfully made the payment via credit card.

That was my most recent experience. Not sure if it would have helped me avoid the issue the first time around, but the chat agent seemed more knowledgeable than the last and he was patient with his assistance.