The avenger vs cannon thingy

Okay, I've spent the entire day replaying that mission, it doesn't even have the mercy to let you lose the game there haha

It seems the game knows your squad is too strong at this point so this mission is the only one that completely disregards normal rules.

E.g. Your scout gets discovered from far away in cover, just because.
And your guys have 75% chance to hit flanked enemies and stuff like that.
I had silly stuff such as 8/10 of my shots missing a Spectre and the entire 10 men squad failing to beat 2 phases of Andromedon. Not sure what to do here really.