Missing shift key in Tor Browser?

This is a very strange issue I ran into while testing on Tails with Tor Browser: sometimes the Signet seems to miss the shift key.

For example, my username will appear as "signet2hax0rbana.org" instead of "signet@hax0rbana.org". This happens about 1/3 of the time.

This also appears to happen with the password field, because it's frequently telling me that the password is incorrect.

This happens nearly every time when using the Login feature (but it does work once in a while).

It never seems to happen when I use the Login feature in a text editor.

When I use the copy to clipboard feature, it seems to always get copied correctly.

My best guess is that the keyboard is going too fast.