I recently started using 1Password X and moved over all major entries from my old password manager. When I then tried to search for a value in an entry which is not the main entry name or most predefined data lines, 1Password X doesn't find it (neither the web-app nor the addon).
Here's an example:
Entry X has the username Y and an additional (added by me) data line Z. If I search for X or Y, I'll find that entry, but if I search for Z, I get no match.
Also: When searching for something, there is no x-button to remove the previous search term so that you have to manually click in that field and delete it.