Rpg Maker Developers Group

I normally wouldn’t post on the forum because I’m shy but I’m actually desperate. I have basically 0 knowledge of JavaScript and can’t solve this by myself. And I don’t know anyone who works in JavaScript!
I’m not sure what caused this, but if I run a Battle Test or trigger a battle during Playtest, I cannot use Attack. I can safely use Guard/Escape/any other option, but specifically cannot use Attack (against ANY enemies). I was fine using Attack before and the only change I have made since then is installing YEP CoreEngine and adjusting some font settings. I think I can say that the problem is the variable “this”, but I don’t know how to fix it.

Here is the error message I receive when I use Attack during combat:

text:
Game has encountered a bug. Please report it.
TypeError: this.startEffect is not a function
at Sprite_EnemyActor.Sprite_Battler.updateSelectionEffect (YEP_CoreEngine.js:2072:44)
at Sprite_EnemyActor.Sprite_Battler.update (rpg_sprites.js:496:14)
at Sprite_EnemyActor.Sprite_Actor.update (rpg_sprites.js:736:37)
at chrome-extension://odlameecjipmbmbejkplpemijjgpljce/js/rpg_core.js:4068:19
at Array.forEach ()
at Sprite_Enemy.Sprite.update (rpg_core.js:4068:19)
at Sprite_Enemy.Sprite_Base.update (rpg_sprites.js:25:29)
at Sprite_Enemy.Sprite_Battler.update (rpg_sprites.js:491:34)
at Sprite_Enemy.update (HIME_SideviewActorEnemies.js:173:39)
at chrome-extension://odlameecjipmbmbejkplpemijjgpljce/js/rpg_core.js:4068:19
Press F5 to restart the game.

I cannot stress enough that I don’t even know how to begin to fix this so please let me know if further information is needed to help diagnose the problem.