Hm ok I'm investigating the RAM usage thing. If you want you can you try running the game with particles disabled, that might have an effect. About a pushback: Might be a undiscovered bug, but is probably melee breakage. Melee weapons all have a limited piercing value and they will break after exceeding the amounts of enemies they can hit in one strike. This will destroy the current strike, throwing you back depending on weapon damage. Light weapons like the Sai or the Katana break more easily, the knife even breaks after one hit, but deals hight damage. Heavy stuff like the Hammer or the Maw basically never break. There are some melee passives that increase piercing.