Apple Magic Keyboard interfering with login

I’ve just moved home and am setting up my new office. When trying to login to the vault for the first time I’m told my password is incorrect - I’ve triple checked and it is not.

After troubleshooting (and successfully logging in using the same password on another device) I’ve found it is my Apple Magic Keyboard being connected that causing the issue.

Disconnected, I can login with my password.
Connected, my username and/or password is incorrect.

Does anyone have any ideas?

My idea is that your keyboard has a fault. If you view the password as you enter it, there are no glitches of any description?

Sometimes my MacBook is plugged into a Studio display in which case I use Apple magic with no problems.