In DayZ Experimental 1.30.164014.27 (and not only), repeatedly clicking “Play” while a connection is in progress produces “The client is already connecting to the server” (0x00030002). If the above condition is met, then after joining the ESC menu will be open, despite player not pressing his keyboard. I was able to reproduce this on both a local vanilla server and official experimantal server 3536.
Also, when the player connects without the ESC menu appearing, the character will rotate on its own and look down at its feet. I have not confirmed whether it always rotates left or always directly into certain direction.
A separate issue of input loss right after the initial connection is resolved by Alt+Tab; its cause remains unconfirmed.