I’ve seen great vault related bugs, but it’s been a while.
I first encountered them during the Shadowlands beta, and despite reporting the bug it seemed like the game was going to go live with the bug still present a week before launch. Luckily I managed to connect with a WoW dev on Twitter and provided proof of the bug. I never heard back after that, but the bug was fixed for 9.0 launch - so yay. However, my assumption is they did a last minute emergency patch and forgot to merge the patch into the 9.1 branch which was already being worked on because when 9.1 went live the bug was back. There’s still a thread from back then with the wow devs acknowledging the bug:
Sounds like whatever you ran into might be a one-off though since doesn’t seem like there’s a bunch of threads about it? Hope you get help from the WoW team…