Your mileage may vary but after 3 months and 2 days (May 19th) and over 4 tickets opened, I fixed the corrupted payment method issue on my own.
The problem started when I added a second oculus to my Facebook account. Immediately the existing payment method disappeared, it forgot the pin, and I was unable to add through the Oculus, Phone App, and PC another payment method or Paypal account. Comparing the console logs from Edge, Firefox, and Chrome the errors that came from the server were identical. Now mind you, despite providing all this to support, I haven't heard a peep from them since June 2nd (and it is August 21st) That said, I think I know what happened and how I unintentionally fix it.
I had Developer Mode turned on for both Oculus'. I went into the Oculus App on the Phone, into Devices, and connected to the newer device. I then looked at the developer setting. I also looked at updates. After that, I went to the store and it just worked. Instead of asking me to log into Paypal or add a credit card, it showed the original credit card (that had disappeared) and I simply entered the pin. When I checked the other oculus the Developer mode showed as a single multiple choice circle rather than a slider. I clicked on it and it reloaded as a slider with it flipped on.
My guess is that code difference between the two oculus' confused the installer and it left the store in a half installed state. When I went to the developer setting or update screen, it somehow freed things up and started asking for a PIN rather than a new payment method. After successfully purchasing through the Phone App, I tried purchasing through the Oculus and again it worked by asking for the PIN instead of asking to input a payment method. Unfortunately this is all guess works as Oculus Support never returns calls, emails, etc.
In short, the problem was the Oculus Store (server) and the Oculus itself (Oculus, Phone App, and web access) didn't agree on what payment method were registered. The Quest thought there were no payment methods set up because it didn't complete the configuration due to differences in code. So it asked for me to enter a payment method. When I added the payment method, this side (Quest, PC, or Phone App) accepted the input and sent it to the Oculus store, but the store server saw that the payment method was already set up, and more importantly no pin was sent (as it wasn't asked for) So the server sent back a vague error and the client software crashed.
So if this problem happens, try going through the Phone App interface and try opening up all the different menu options as that seemed to kick something loose in this case. This time it was the update or developer screens. However, this problem existed before the Facebook purchase and thus depending on when you see this, it might be another installer/cache conflict.