Hi Inge. I'm Greg, 10 years awarded Windows MVP, specializing in Installation, Performance, Troubleshooting and Activation, here to help you.
Have you tried a wired keyboard, just to rule out that it's a Windows issue?
I'll give you everything to go over a keyboard to try to find and fix most problems, but if it doesn't work then I'd assume the problem is the transmitter. If it's within a year of purchase Logitech Support can try to help you fix it but if not then they need to replace it under warranty.
Here is everything to try to fix a keyboard:
Run the Hardware Troubleshooter:
Type CMD in Search box, Run Command Prompt as Administrator, copy and paste or type the following command followed by Enter key:
msdt.exe -id DeviceDiagnostic
Run the Keyboard Troubleshooter at Settings > Update & Security > Troubleshoot.
If this began within the recent past, See if you can System Restore to a point before the problem began:
https://www.windowscentral.com/how-use-system-r...
Check which Updates were installed at Settings > Update & Security > Windows Update > Installed Update History and try uninstalling any from around the time this started. If they return and cause the same problem then hide them with the Hide Updates tool:
https://www.tenforums.com/tutorials/8280-hide-s...
If this was caused by a Version Update then for 10 days you can roll it back in Settings>Update & Security>Recovery and then hide it until it matures using the Hide Updates Tool.
What also might work is to go into Device Manager, reached by right clicking the Start button, choose the Keyboard device, on Driver tab try Updating the driver automatically.
If this fails from the same location try rolling back or Uninstalling the Keyboard driver, which works in a surprising number of cases where keyboard is messed up by Updates. Restart PC to reinstall driver.
See if the On-screen Keyboard works at Settings > Ease of Access > Keyboard > Turn On the On Screen Keyboard.
If the problem doesn't repeat itself in the On Screen Keyboard then it means there's a hardware issue with the key. Try cleaning the keyboard and/or removing the key to clean underneath:
https://www.wikihow.com/Clean-Under-Laptop-Keyb...
https://smallbusiness.chron.com/clean-under-lap...
Try resetting the keyboard:
http://www.thewindowsclub.com/reset-keyboard-se...
You can also remap keyboard keys using one of these methods:
https://www.makeuseof.com/tag/missing-key-remap...
https://www.pcmag.com/how-to/how-to-remap-your-...
Customize keyboard layout as shown here:
https://www.makeuseof.com/tag/create-custom-key...
https://www.addictivetips.com/windows-tips/inst...
Bind keys to certain functions as shown here:
https://grayishgames.com/pc-key-binding-for-beg...
Try plugging in a USB keyboard to see if it does the same thing.
I hope this helps. Feel free to ask back any questions and keep me posted. I will keep working with you until it's resolved.
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