[Error] Every battle instantly crashes, what does "Given 2 arguments and expected 0" mean?

[SuperSpyroDragon64]

Hi, this is the error message and I have no idea what it means. I get this error message whether I try battling the default NPC "Camper Liam" that came with Pokemon Essentials or the default NPC "Brock".

[Pokémon Essentials version 20.1]
[v20.1 Hotfixes 1.0.2]

Script error in event 23 (coords 26,8), map 3 (Player's house)
Exception: ArgumentError
Message: wrong number of arguments (given 2, expected 0)

***Full script:
TrainerBattle.start(:CAMPER, "Liam")
Backtrace:
172:Battle_Move:59:in `initialize'
172:Battle_Move:59:in `new'
172:Battle_Move:59:in `from_pokemon_move'
161:Battler_Initialize:89:in `block in pbInitPokemon'
161:Battler_Initialize:88:in `each'
161:Battler_Initialize:88:in `each_with_index'
161:Battler_Initialize:88:in `pbInitPokemon'
267:ShadowPokemon_Other:196:in `pbInitPokemon'
161:Battler_Initialize:61:in `pbInitialize'
148:Battle_StartAndEnd:117:in `pbCreateBattler'

This is his script, and it should work.

TrainerBattle.start(:CAMPER, "Liam")

And that's all there is to his code. No matter what battler NPC I talk to, the game immediately crashes.

edit: Found a new error message!

[Pokémon Essentials version 20.1]
[v20.1 Hotfixes 1.0.2]

Script error in event 5 (coords 27,4), map 3 (Aaa's house)
Exception: NameError
Message: wrong constant name Battle::Move::

***Full script:
TrainerBattle.start(:LEADER_Brock, "Brock")
Backtrace:
172:Battle_Move:58:in `const_defined?'
172:Battle_Move:58:in `from_pokemon_move'
161:Battler_Initialize:89:in `block in pbInitPokemon'
161:Battler_Initialize:88:in `each'
161:Battler_Initialize:88:in `each_with_index'
161:Battler_Initialize:88:in `pbInitPokemon'
267:ShadowPokemon_Other:196:in `pbInitPokemon'
161:Battler_Initialize:61:in `pbInitialize'
148:Battle_StartAndEnd:117:in `pbCreateBattler'
148:Battle_StartAndEnd:153:in `block (3 levels) in pbSetUpSides'