1Password Sometimes Double-Fills Password Field

I have this issue too on multiple sites. This is the website I just had the issue with: https://moneybird.com/login
My flow and info:
- firefox latest update, 108.0.1, 1password 8.9.12, BETA channel, addon version 2.5.1
- enter the website in a new tab
- command-\ (my shortcut for 'fill')
- username and password fill both; in the password field I see the amount of stars corresponding to the length of my password
- within one or two seconds, the amount of stars doubles

Additional:
- 'inspect elements' after the 'doubling' shows it concatenates the correct password to itself, actually filling the field twice
- if i submit within the 2 seconds (i.e. before the 'doubling') login works fine
- This doesn't seem to be predictable - i.e. logging out, closing the tab, doing it again doesn't always show the same behaviour
- I have this on multiple sites
- If I do command-\ again after the doubling, the original password gets entered again, and the doubling does not occur