Relay Station TRS-150 Fan Bug?

We were playing Level 4 Low Intensity mission and got to the Fan event. We had placed all three cells and were fighting a wave just in front of the fan, before we could stop it. A hound and trapper both came from behind us, through the spinning fan, and downed the three remaining of the team. It really sucked since we had made it so far on this difficulty.

This can’t be by design, right? If anything, it’s super immersion breaking.

Snipers can shoot and bombers can throw grenades through the fan after pressing the buttons but before the fan stops too.