Why did copying by cmd-c combination stop working on mac?

Question

macOS

Hello!
Today a strange thing suddenly happened - copying to cmd-c stopped working.
If you copy from the context menu, everything is ok.

The "C" key itself, as you can see, works.

All other commands - cmd + x / z / v / f / s / a and so on work fine, that is, cmd is also alive.

Has anyone experienced this?
I did not install anything new, I did not touch any settings.
Restarted mac, restarted pboard, closed all programs - all to no avail.

macOS 10.13.16 Keyboard
native, wired Apple USB Wired Keyboard A1243

UPD: I connect a regular keyboard - copying works fine on win + c
UPD2: Turned on "Sticky Keys" in accessibility. In this mode, it turns out to copy if you press cmd - release - press c
UPD3: Resetting NVRAM / PRAM did not help
UPD4: For some reason, if I change cmd to something else in the modification key settings, for example, to the same ctrl, it does not work nothing from ctrl+c/x/z/v/f/s/a
UPD5: In safe mode, the problem remains
UPD6: I noticed that the first 20 seconds copying works

Answer 1

If suddenly someone gets into the same situation, a deep cleaning of system caches with the help of the Onyx program helped .