Hacking
Just played a match where all 4 survivors were speed running, putting themselves on the hook anywhere (and not counting) , and instant heal.
During the match the game would periodically "pause" like something was going on with the servers. But the fact that so much abuse is possible is troublesome.
Comments
I hope you recorded and reported them in-game, then sent the recording to Support. Unfortunately, every multiplayer game has cheats.