Reproduction:
- Click LAUNCH or press Return/Enter to bring up the flight assignments window
- Click ENGAGE for PVP/PVE/SQ match-making, the “Searching…” queue window comes up
- With the chat window closed, press Return/Enter to bring up the flight assignments window again. You stay in the queue until you try to queue again, which will pop an error message and kick you out of the queue.
tl;dr: While queued those hotkeys should bring up the queue window or be disabled.