Open Device Manager and uninstall the keyboard and reboot. On reboot, it should be reinstalled. This may/may not help, just a starting point.
Reference: https://answers.microsoft.com/en-us/windows/forum/all/windows-10-keyboard-repeat-rate-went-from-normal/ad4ca76a-348b-4379-9129-9a7ede0a1e36
A...