Kickstarter login autofill not working

I’m using 1Password 8, and some time in the last few weeks, autofill using the extension stopped working on Kickstarter. It offers my login in the dropdown in the username field, but no matter how many times I tap my username, it doesn’t fill in. For a while, it sometimes would show filled if I reloaded or submitted it empty, and then I could finish logging in.

It still works using the password extension from the predictions bar, though. I’m not sure how those two differ, but I guess they must.