Hi Georgian,
Welcome to Sony Community!
We're sorry to hear about this. Thank you for providing helpful information. The driver used for the on-screen keyboard is different from the actual keyboard that's why the former worked flawlessly. We can also isolate the issue by using another keyboard (desktop keyboard) . If it worked without any problem then it is the built-in keyboard that has a problem (hardware).
For hardware related issues, service is needed. Here is the link for repair information.
Regards,
Jen
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