Spectres in Mansion: Coming with an alternating immunity shield, self-heals and regen, stuns, roots and a proclivity to scatter, they will almost certainly wipe you if coupled with snipers.
Invisible spawn waves: Mobs will often not render for several waves, or an entire scenario.
Invisible snipers. Crosshair icon will not always render. Survivors still will hook on Snipers, and sometimes be shot in return.
Mobs hiding INSIDE geometry, mostly in Hotel: ranged pistol cultists will frequently run INSIDE the stairs, becoming immune to all attacks or pushes.
darxide: This happens in the Mansion when specters come up. They can phase through the back porch in the South East (I think it’s SE… I’ll have to double check) corner of the Mansion and just sit in the and attack survivors. You can’t hit them, even with AOE. Luckily, survivors and turrets can hit them, but only if you’re lucky enough to have a turret or a survivor with a weapon over there.
Giving survivors melee weapons makes them difficult to manage (Feedback, not a bug report)
(More Feedback: we need a group mode so badly.)
[Mod edit: Moving to bug reports, removing editorializing of reports to keep them objective.]
(I want a ‘Pillar of Salt’ badge.)