Some bosses can still kill you after they've been defeated due to not giving the player invicibility or not despawning the boss' attacks. Some prime examples are Dominique's lingering Va Schia, 8 Bit Overlord's lingering fire pillars, Zangetsu mode Miriam's lingering sickles and almost every boss in boss rush mode.
Sometimes Zangetsu 2 warps under the floor of the battlefield when triggering his black hole attack, softlocking the fight.
Orobas's jumping back attack is lacking the fire projectile shot on nightmare difficulty specifically, despite working fine on hard mode.
Quickly exiting the OD boss room and re-entering it allows the player to move during the dialogue and drain the boss's health before the fight.
Fire pillars created by Fire Elementals and Orlok Dracule have a wonky hitbox that can hit you when you're besides them while in the air.
A few enemy patterns are actually framerate dependent such as the Plume Parma's charge attack and IGA's 360 degrees wineglass attack, those will play at insane speeds if the user has uncapped FPS.
Invulnerability frames after getting hit by environmental damage start counting down much earlier if the player was knocked into spikes by an enemy attack instead of simply falling into them.
Adversity Ring does not work as intended, instead of increasing every stat by 20% it adds a set value of 0.2 to all of them when under a status effect, essentially doing next to nothing.
Money is Power and Red Rememberance only boost the starting stats + level up stats, ignoring stats obtained from gear or food bonuses which makes those shards next to useless on nightmare difficulty.
The Shadow Tracer shard has an issue where the duplicate's attacks have a set damage value instead of taking a portion of the player's attack when used with guns, rava weapons and heaven swords. 15 at grade 1 and 22 at grade 9.
The breakable wall in m17RVA_003 shares the same drop ID as the one in m17RVA_011.
The timer for the lifetime of Bael's tracer ray also counts down while the player is in the pause menu, so pausing while the laser is out will despawn it early.
Getting crushed by the rotating cog platforms in m08TWR_013 does not damage the player, instead it allows clipping through them and skipping the room entirely.
Occasionally some room ambient sounds will fail to stop playing when transitioning to the next room and linger forever until the file is reloaded.
Some platform graphics are not lined up with their respective collision such as B_JPN_Pillar00_00_XZ12 in m15JPN_010_BG and B_BIG_Side_x1_z1_299 in m10BIG_017. Bael's purple platforms also have a much thinner hitbox than they appear.
Some stained glass windows in the background of m05SAN_009 are not lined up with the arches, leaving black holes.
The VFX for Bael's flameskull explosions briefly shows a square white transparent texture that doesn't belong.
Some bosses have a different crystalization color than the shard they give, for instance Valefar and Gremory become red despite giving purple shards and OD becomes white despite giving a blue shard