Unfortunately all disconnections and game crashes counts as leaving the match and will be penalized appropriately. The game server has no way to discern a legitimate disconnection or game crash from one that is forcefully caused by a dishonest player to bypass leaver penalties. You can learn about this policy here:
Since you have identified the issue, I will spare the troubleshooting. Hopefully this helps explain why this policy exists and how it helps ensure a better competitive experience for everyone. Cheers! (^^)v