Please refer to the attached gif file illustrating better how to replicate the undesired behavior.

1. If you right-click, the Copy and Cut context menu items are disabled - OK

2. If you select some text and right-click, the Copy and Cut context menu items are enabled - OK.

3. If you select some text and right-click very fast, sometimes Copy and Cut are disabled. Even there is cases in which Cut is enabled and Copy is disabled. 

Workaround: please ensure that you select the text first and then right-click to trigger the context menu.