The Windows shortcuts are mere theotherways of doing the exactly same things that are available via the context menu, as far as I understand.
So it is very much unlikely it is something related to the browser, though I can be wrong, of course.
But as long as the shortcuts are in question, there might be a simple explanation: like your C or V key fails time to time - like there is a piece of shit having fallen under there some time ago, or any other mechanical problem. :sherlock:
It's too bad that I cannot add attachments here.
If you had read the Posting Guide you would know how to do it.
I noticed that the colors of a presentation stored in odp format [using LibreOffice Suite] changes colors, from that originally saved, when trying to view it within the browser.
Only on those files?
Maybe related to the issue discussed on this topic