@Jim_Harman - the previous thread on this topic (linked below) was closed so I have to ask you this in a new thread.
I thank you for the steps you provided. I've been haunted by this issue for a VERY long time (years) and have always just worked around it and hoped I was doing it correctly. I contacted Quicken support today about OSU messages indicating downloaded transactions from Vanguard that weren't showing up, and they made me deactivate and re-add all my Vanguard account (7) which brought the problem back again.
In your steps, you reference an "outage" and say to look at a backup from before that outage to affirm the "old" account numbers. What if I have no idea when Vanguard switched my accounts (the 2 problematic ones) from old numbers to new numbers - how do I find those "old" account numbers? (You say they'll begin with 2 digits and a "V" - but mine might begin with "AVV" ?)
Also - any idea if there's any way to get Vanguard to stop sending down data to Quicken for an account that apparently no longer exists (doesn't show up when I log into Vanguard.com) ?
Thank you - as always - for any help you can provide.