Is /MyAccount/vault/ buggy? It occasionally returns everything with no itemInstanceId

I have been losing my mind with an intermittent bug, but it turns out that /MyAccount/vault/ will occasionally return the vault contents but nothing has an itemInstanceId. Here is a snippet from 2 requests request 1: {"itemHash":2217280775,"bindStatus":0,"isEquipped":false,"itemInstanceId":"0","itemLevel":48," ... request 2: {"itemHash":2217280775,"bindStatus":0,"isEquipped":false,"itemInstanceId":"6917529062000077190","itemLevel":48 You can see in the 2nd request it does correctly have an itemInstanceId. I have not been able to do a ton of testing, but this seems to occur once you have 65 or more items in the weapons vault.