Do you have the possibility to test the keyboard on another device (Windows PC/notebook)? If the problems are also present there, then in my opinion this would be a warranty case.

According to our information, we unfortunately do not offer replacement feet.

never had any problems, the keyboard and mouse communicate with the corresponding USB Sick, which requires the standard USB driver of WIN X, use good and new batteries for both devices. Good luck!

Unfortunately, we do not offer these separately.

I couldn't find a Cherry dongle to order separately. Maybe you can spoil it with a universal one.

Not that I know of. I've solved this on other keyboards with two rubber buffers from the hardware store that I stuck under the keyboard. That works fine.