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I have an external keyboard (Logitech K120, Windows Layout) connected to my notebook, running Windows 10, and since today I am facing problems when using shortcuts that involve Ctrl+Shift.

One concrete use-case that I have and struggle with is selecting whole words per short-cut, i.e. "Ctrl+Shift+Left or Right Arrow". On the built-in keyboard that works, on the external only with Ctrl+Shift on opposing ends of the keyboard.

Specifically, if I want to use them I have to use the keys on opposing sides of the keyboard.

The following do work, but in my opinion make for a very awkward hand-positioning:

  • "Left-Side Ctrl + Right-Side Shift + Arrow key"
  • "Right-Side Ctrl + Left-Side Shift + Arrow key"

The following combinations don't work:

  • "Left-Side Ctrl + Left-Side Shift + Arrow key"
  • "Right-Side Ctrl + Right-Side Shift + Arrow key"

I checked the following scenarios which all worked fine:

  • Try the shortcuts on the built-in keyboard of the notebook
  • Try the keyboard on another computer
  • Try another keyboard on the notebook

Therefore I assume, that it is a driver issue. But uninstalling the keyboard via the device manager did not work.

The problem coincides with two things: On the notebook an update of the MS Office Suite to Office 365 took place and the keyboard was attached to a Mac. I somehow doubt, that this actually has to do anything with each other, but maybe it is useful information.

I would be really glad for any kind of information how this problem could be solved. Thank you.

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  • looks like keyboard ghosting/key rollover issue
    – phuclv
    Commented Sep 25, 2023 at 9:56
  • What is the expected behavior when holding down two keys on a keyboard?
    – phuclv
    Commented Sep 25, 2023 at 9:59
  • Hello @phuclv thank you for your reply. But I don't think this is the issue here. Maybe I didn't make it clear enough in the text, but the shortcuts in general do work but not if I use the Ctrl and Shift keys, that are located on the same end of the keyboard. If I use the opposing keys, i.e. "Right-side Ctrl + Left-side Shift" it works fine. I will add this clarification to my question.
    – Christian
    Commented Sep 25, 2023 at 10:21
  • yes that's exactly the behavior of key rollovers. Because keys close together use the same line in the matrix, causing the inability to differentiate them. Although rolling over 2 common keys like Ctrl and Shift is weird
    – phuclv
    Commented Sep 25, 2023 at 12:19
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    @phuclv But the thing is, it was working with this exact same keyboard previously and is still working if I attach it to another computer. This wikipedia article in the one post suggests to me, that the rollover is a hardware issue, so my problem should occur regardless of where I plug it to.
    – Christian
    Commented Sep 25, 2023 at 12:36

1 Answer 1

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I managed to solve this problem myself and maybe the solution (though, nobody could have given it to me here, because I didn't realize nor mentioned that this actually changed) will help somebody, that will stumble over the same issue.

The keyboard is attached to the computer via a kvm-switch that has 4 USB-sockets, two of which are marked USB-2.0 and the other two as K/M for keyboard and mouse (I don't know what this means in terms of a USB version, probably something older).

Apparently, earlier the keyboard was attached to one of the USB-2.0 sockets but then I mixed it up and attached it to the K/M-sockets but they seem to have caused the problem.

After attaching the keyboard back to the USB-2.0 socket everything works fine now.

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  • It's possible these K/M allow the switch to act as constantly connected keyboard+mouse for each computer. A device connected to a general-purpose USB vanishes from one computer when it gets attached to another. For a keyboard or a mouse this may be problematic in some circumstances (e.g. "no keyboard detected" error at boot). Therefore the switch can pretend to be a keyboard and a mouse all the time for all computers, but only relay events from actual keyboard and mouse to the chosen computer. I guess in your case the issue was in this layer. Connecting to a general-purpose USB bypasses this.
    – Kamil Maciorowski
    Commented Sep 26, 2023 at 7:16
  • Compare to this answer.
    – Kamil Maciorowski
    Commented Sep 27, 2023 at 17:02

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