Sometimes the file browser of my Lubuntu OS(PCManFM) doesn't accept `Ctrl`+`C`/`Ctrl`+`V` commands. I have to copy files using the mouse. `Ctrl`+`X` have this random problem as well; furthermore icons of files selected to be cut doesn't change (usually file browsers apply transparency to icons of cutting files). 

I have not found a known open bug. Maybe keyboard is misconfigured?