CommonEvent 884 calls:
LNX11.ポップアップ([:actor, 0], 100,
:hp_damage, :hp_damage, :hp_minus)
which is a custom script for showing HP or MP damage in a certain style.
hp_damage, hp_minus don't exist for the last 2 args
the call should be:
LNX11.ポップアップ([:actor, 0], 100)
Since the script defaults to HP damage, args for mp_damage/mp_minus are only ones needed.
Not sure why it broke in 2.0e and I haven't bothered to look at earlier versions. I'm guessing either Ahriman goofed when updating the script or maybe he copy/pasted in commonevents, then changed mp->hp without realizing it's not needed