This is something that I've been noticing for quite some time; If you re-queue for a ranked match but dont leave the end-game lobby before the timer reaches zero, the game will fail to join the new match if it was trying to connect at the time you are kicked back to the main menu. I see this happen pretty frequently which makes me think that matchmaking efficiency could be improved significantly with a minor tweak to the system.

Joining a new game with ~3-5 seconds left on the countdown timer at the end of a match reliably causes a failure to join the new game when the game ends and drops you to the main menu. This cancels the match queue for everyone who would have gotten a match if you had joined, and puts you and them back into the join match queue to wait until another matchmaking cycle finishes. (This probably corresponds to the failure message of 'not all players connected' showing up in everyone else's join queue.)

It seems like the code that kicks you to the menu should defer priority to the join queue. Instead of quitting the map you are on to load the main menu exactly when the countdown hits zero, it should check to see if you're joining a game first. If so it should not kick you back to the main menu but should stay on the map and join the new game instead. Forcing you back to the menu while in a countdown to join a game causes the connection to that game to terminate, so if the game stayed in the server for those extra couple of seconds it took to load the new map it could increase the efficiency of matchmaking and reduce queue times for everyone.

System Specs:
OS: Windows 7 x64
CPU: Intel i5-4670k Quad Core
RAM: 24 Gigs
SSD: 512 gig Samsung 850 EVO
NET: 112mbit download / 10mbit upload