I've only tried this on one site so far, so I'm not sure if the problem is with the Beta or the website. When asked to fill in my credit card information to make a payment, I first tried the new feature of selecting the 1password icon in the credit card number field. Nothing filled, but the screen started to flash repeatedly, like it was trying to load and display over and over. I then cancelled the transaction and went back in trying the old autofill way. Same screen flashing response. I rebooted my PC to see if that might have been needed after the upgrade and tried the above steps with the same results. In the end, I completed my payment transaction by copy and pasting each field from my 1password to the safari screen.
1Password Version: 7.7.Beta-0
Extension Version: build #70700000
OS Version: OS Catalina 10.15.5
Sync Type: iCloud