Hi,
Please try if the same thing will happen as well in your on screen keyboard. To bring up on screen keyboard press Windows + R together at the same time then type in "osk" in the Run box that will open. If it's still the same you need to try to uninstall and reinstall the keyboard in Device Manager, here are the steps on how to.
- Press Windows + R then type "devmgmt.msc" in the Run box and click OK
- Expand Keyboard then right click on depending what would show there under keyboard then select uninstall.
- Reboot the PC after uninstalling the keyboard driver.
- Once back in the desktop try the backspace button again.