Hello Lazzand!
Thanks for using the Apple Support Communities!
I see from your post that when you try to use your Shift keys on your Mac, your Mac doesn't always register them being pressed.
Testing for the issue in a new user was an excellent isolation step. I'm glad you've been so proactive in trying to resolve this on your own.
If you haven't done so already, take a look at this article called If your Apple keyboard doesn't work, and try these steps:
You might have set an option that changes how your keyboard operates. Choose Apple () menu > System Preferences, and then try these tips:
- In the Accessibility pane, click Speech in the left side. If "Speak selected text when the key is pressed" is selected, deselect it or click Change Key to select another key.
- In the Accessibility pane, click Keyboard. Make sure Enable Slow Keys is turned off. If it's on, you have to hold down a key longer than usual before it's recognized.
- In the Accessibility pane, click Mouse & Trackpad. Make sure Enable Mouse Keys is off. If it's on, pressing keys in the numeric keypad moves the pointer instead of entering numbers.
- In the Keyboard pane, click Input Sources. Make sure that the correct keyboard layout is selected.
You can also see your keyboard's current layout on your Mac's display to make sure that you're using the correct layout:
- In System Preferences, click Keyboard, then select "Show keyboard and emoji viewers in menu bar."
- Choose the keyboard icon
in your menu bar, then choose Show Keyboard Viewer. You'll see a graphical representation of your keyboard that highlights the corresponding keys you press on your keyboard.
If the issue continues to persist, contact Apple Support.
