Valentin-N
commented
2 years ago I can confirm this behavior, but I don't think it's solely related to locking as I can trigger the same exact behavior by focusing on any password input box (e.g. a login form in the browser). I assume the lock screen is a special case of the password input box. I don't know what special input behavior this elicits in MacOS, but it seems consistent for me across apps, MacOS versions, etc.
Previous discussion on related issues that I think share the same root cause:
After locking the screen (no matter how you do that - from laptop or from a bluetooth keyboard, also no matter how you unlock it - with a Touch ID or with a password) I'm getting my keyboard input duplicated (checked in EventViewer). In fact, the duplication starts immediately with a lock key pressed (meaning that it is the first one which is duplicated). This only happens when Karabiner Elements is running. Although in most cases this doesn't affect anything (the sequential input is ignored mostly), but for example Lock button starts locking the screen immediately instead of requiring you to press it twice. MacOS requires you to press it twice just to avoid locking the screen if you press this button by mistake - and this prevention now doesn't work with Karabiner.
My macOS version is Monterey 12.0.1 on MacBook Pro (16-inch, 2019).
P.S. I can reproduce it in 100% of cases. Even when Karabiner doesn't have any user-defined settings (i.e. default installation).