Today I created a new Login, then entered CONTACT in the first custom Section and set the first custom field to Phone. Then I went to a web page to copy the phone number. When I switched back to 1Password, the Section and Field had duplicated themselves. Oh?
This has happened on more than one occasion. Though I can't tell you if it's new to 7.4.3 or first appeared in 7.4.2. I deal with it by clicking on Save, then Edit, then using the delete widget to remove the extra Section/Field.
1Password Version: 1Password 7 Version 7.4.3 (70403002) 1PWD Store
Extension Version: 220.127.116.11
OS Version: macOS 10.15.4
Sync Type: iCloud