I think I may have seem a thread similar to this, I just couldn't seem to find it. It would seem that when using a quick command that requires input after issuing the command, the quick command is repeated as input. As an example; I use "AA" as a quick command for AUDIT. After issuing the "AA" command, AA seems to be automatically entered as the input to the input request "Fix any errors detected?". That occurs without me typing anything. I've yet to find a way of reproducing it constantly. Sometimes is occurs, sometimes not. When it does occur, and I press esc and enter to repeat the command, the request for input "Fix any errors detected?" is blank, awaiting my input. AA is not the only command that this occurs with, the the most common and recent. This also occurs with the quick command for -PURGE, "-pu", and a couple others.
Shortcut - quick command - semantics.
No Dean, no problem with mouse or keyboard or any other strange assurances, no demon possessions (that I'm aware of). As I've watched it (or I guess when I was using 2015 and watched it) I typed AA, hit the space bar, the prompt "Fix any errors" appeared with AA at the prompt. I am not double tapping the keyboard or enter or right mouse button. Yes, it would seem this is the only "shortcut" for which this occurs. It is, I believe one of those special mysteries Autodesk has provided, somewhat akin to turning off autosave arbitrarily, just to keep us on our toes.