Universal Autofill stopped working on Quickbooks Online

I have a standalone app for QuickBooks Online on my Mac, which was created by going to QuickBooks Online in Safari, then choosing File > "Save to Dock...". For quite a long time I've been able to log in within that app by using 1Password's global keyboard shortcut to trigger the universal autofill.  A month or so ago it stopped working. It always results in a password failure. But if I copy the password and paste it in, it works fine.

QBO has an option to show what's in the password field, so I turned that on, and it shows that about half of my username (not the entire username, and it was the latter half of it) ended up in the password field in front of my password. There is actually no username field on that page, it's only prompting for the password itself.

Universal Autofill has continued to work fine in other web apps that I have in standalone app containers like this.