This isn't a Bugg - This is clearly working as intended.

It's obvious to me that your using Dutchess on your team.

Are you aware Dutchess was on the Nerf/Buff Rebalance List.

At first, The game was going to Nerf Dutchess thinking she was to strong.

In the end, The game decided to Buff Dutchess realizing she needs to get stronger.

What you are seeing is the Ultimate Veil Buff.

Ultimate Veil Buff is almost like Perfect Veil Buff except your whole team is invisible.

Think the screenshot basically speaks for itself - the fight has moved on to round three, but my camera view hasn't... I was running FK20 on semi-auto, letting the waves run on auto but switching between manual and auto for the boss fight. Here I switched from auto to manual right as the game went from round 2 to 3 - so the camera stayed behind. Battle continued normally, except that since I couldn't see or target the boss, there was no way to manual the fight and I had to let my team suffer an inevitable defeat on auto (speaking of which, any plans to ever make champion AI take into account the FK's shield?). 

Maybe one of the many bugs related to the patch.