If Lash gets pulled by Rescue Beam, Hook etc. while casting Ground Slam, you can no longer use any ability, shoot nor jump. Pressing unstuck or suicide, or restarting the game does not work, game is just over for you.
This glitch is still alive and well. Just had a contentious match ruined by it. Interestingly, our Lash could get unstuck by being stunned by Seven, but then he just got stuck again in the next teamfight :X