This behaviour is bugging me recently and I decided to post here after noticing it is still happening when I upgrade from 6.4.6 to 7.0.4.
When and use Control+Anything Libreoffice does the action twice.
For instance, control+v pastes twice the content of the clipboard.
I thought this could be a system issue, but it only happens in Libreoffice apps (Writer, Calc, Impress).
I found a few people reporting something similar on other forums, but no solution so far.
I am using Libreoffice 7.0.4 in KDE Neon 5.20.