Query on BNK-3R Buster Challenge

I can’t see how to complete the BNK-3R Buster challenge. The game requires you to destroy all the cannons before the BNK-3R starts to fly. I tried to destroy the BNK-3R before it took off, but this had no effect what-so-ever. Is there something I am missing?

knighm

I think you got it wrong. You’re supposed to destroy the Bunker without killing any of its on-board autocannons.

Just aim for crits on the eye of it, if there’s a shield, go nearer, that should drop the shield.