Just upgraded to 1Password 7 from 1Password 6 - missing the last two years of password updates

I've been using 1Password 6, using Dropbox to sync. My 1Password vaults are in the .opvault format.

I signed up for 1Password 7, installed the app, and it appeared to import my vaults. But when I tried to use it and logins started failing, I saw the most recent updates in the vault were from 2018. That is around the time the vaults changed format (.legacyagilekeychain). It looks like the upgrade grabbed the last good copy of the old vault instead the current vault I am using.

I was able open the current .opvault by double clicking it. I can access it in 1Password 7, in Vaults under "On Dropbox".

I was able to Import -> 1Password6 -> and browse to the sqlite file, but when I do this I now have duplicates.

How do I get rid of the obsolete data in the new 1Password vault, and how do I move the Dropbox vault to the new 1Password online vault? Is there a way to start over and get it right?

How can I avoid this when I go to my wife's computer and upgrade her 1Password?

The upgrade process has been very very painful so far.

1Password Version: 7.7
Extension Version: Not Provided
OS Version: 10.14.6
Sync Type: Not Provided