Editing generated passwords skips the cursor to the end.

When adding a new account using the Safari plugin, I have historically used the "generate password" feature and applied minor edits to the result until I end up with the password that I actually want to use. That worked fairly well until recently, when an update to either Safari or the 1Password extension seems to have changed how the input field works. Now, every time I add or a delete a character in the generated password, my cursor is kicked to the end of the field. That's makes any modification of the generated password extremely difficult.

For example, if 1Password generates "sha5whe5re6cu," I might try to add some punctuation after "whe." As soon as I type that punctuation, my cursor jumps to the end of the line (past the 'u').

Is this a known issue? Can I do something to avoid it?