That red thing is bloody wave intended to kill you send my Manduka (boss after defeating level 1 that's far more dangerous then normal zombies it had different type of move sets too)
That would be a bug probably.
Yes it's possible to survive first wave, and it's easy actually if dash js used wisely. Many people managed to even defeat the boss at the end of the game (if you haven't seen the boss I suggest to check the recording on the itch page)