Escape from Castrum Centri bug, Magitek Vanguard H-1 Invulnerable

[Sensu]

Tonight I tried to infiltrate Castrum Centri to free the Scions, but at the part where I had to untie them, I chose to defeat the enemies first and I would untie them afterwards.

Though, when the last enemy went down here, a cutscene popped and it progressed the Quest. Everything seemed normal, until I went outside where Wedge went off to fight a group and I stay behind with Papalymo and Uringer. A group of Imperial soldiers greets us, including a Magitek Vanguard H-1. My goal now is to defeat the pack and escape, but everytime I attack the H-1, it says invulnerable and I can't seem to do anything about it. All the enemies went down and I wasn't able to harm him in any way.

I relogged and now I can kill him, but still... I don't think thats supposed to happen.

Edit: Sorry, the actual bug I'm reporting is that they didnt shout for me to demolish the shield generators. As they didnt call out for me to destroy them, I wasn't able to.