I'm currently on MacOS 10.13.6 using Chrome (Version 73.0.3683.86 (Official Build) (64-bit)) and Safari 12.0.3 (13606.4.5.3.1) 1Password 7 Version 7.2.5 (70205002) AgileBits Store (1Password.com account converted from standalone app) Chrome 1Password Extension 126.96.36.199 and Safari's extension ver 7.2.5
I believe that Chrome behavior below is the same (at least end result is same) on my Windows 10 (1709) PC.
Goto my login item for my.scouting.org which has the following as the website, and it immediately goes to the recover password and username page and fills in just my username.
I see the main login page for that site as it flashes by on its way to the recovery page.
Seems to be running a script and the URL at the top never changes from https://my.scouting.org/
If I manually copy username and password from 1Password to the main login page it will log me in.
Same behavior if using extension or app ie: click item and it launches and fills it as described above.
Slightly different behavior in Safari:
Using Safari's extension (ver 7.2.5) it says on the main page but does not fill in the username, says "The username field cannot be blank" and seems to fill in the password (but I can actually tell its the username because if I manually copy the username from 1Password and pasted it then click login, it does log me in)
Maybe similar issue but not even getting to "dashboard-legacy" unless I manually copy the username and password
1Password Version: 7.2.5
Extension Version: 188.8.131.52
OS Version: MacOS 10.13.6
Sync Type: 1Password.com account