One possibility is that there may be a security feature or setting enabled on your MacBook Pro that's causing the lockout after a single unsuccessful login attempt. Some security settings, such as those related to FileVault encryption or system preferences, could potentially trigger a lockout after a certain number of incorrect attempts, even if it's just one.
Additionally, since you mentioned using a security key, it's worth considering whether there might be any interactions or conflicts between the security key and your login process that could be causing the lockout. Ensure that the security key is properly configured and recognized by your MacBook Pro, and check for any updates or compatibility issues related to the security key software or firmware.
If you're unable to identify the cause of the lockouts or if they persist despite troubleshooting, it may be beneficial to reach out to Official Apple Support for further assistance. They can provide more specialized guidance and potentially investigate whether there's a specific issue with your MacBook Pro or its settings that's causing the lockouts.