Using 1Password on the Mac, I am a member of a team. The team-supplied passwords are hidden from me (no option to reveal). All I can do is launch a website using one of those passwords, and that's fine.
However, if a password from a Team vault matches one in a personal vault, I can see which entry, and thereby learn the password for the entry in the Team vault. (Obviously this won't be an issue with random generated passwords, but not everyone's there yet.)
The solution would be to suppress the check for duplicated passwords, for entries that you don't have view permission.
1Password Version: 7.3
Extension Version: Not Provided
OS Version: OS X 10.14
Sync Type: 1Password