My issue is an exact duplicate of https://discussions.agilebits.com/discussion/40090/sync-bug-in-1pw-android-with-passwords-converted-to-logins-known-issue (other than the model of phone). All replication steps are the same.
My Mac is running 1Password 6.5.3 and Sierra 10.12.2.
My workaround is temporarily copying the password to a note on MacOS, and copying it from the note to the login password field on Android.
As of April 2015, @peri reported that this was a known open bug. Is it still open?
1Password Version: 6.4.5
Extension Version: Not Provided
OS Version: Android 7
Sync Type: Dropbox