Hello - as a start, make sure to get the latest driver from the NVidia website - 2016 is getting pretty old, and and V6 makes pretty heavy use (more than 5) of the video card. That might just clear up the speed issues - we shall see.
As for the other things -
Issue 2: Sometimes after selecting object, “enter” does not work or freezes
Does this mean, inside a command, the user is prompted to select and Enter does not end the selection and carry on with the command? If that is it, can you ask the user if it is command-specific or at least if there is one command that shows the problem? I’d like to test that…
Issue 3: After selection losing property dialog box
I’m not sure what this means exactly - Is this outside of any command, just selecting? Is Properties open (Docked or floating?) and it closes? Or moves behind another panel?
Issue 4: Sometimes cant delete after selecting an item
So, just select and item and hit the Delete key? No command running?