Press F8 when the error occurs and copy the error log.
TypeError: Cannot read property 'call' of undefined
at Function.BattleManager.tickRate (/C:/Users/Joshya/Documents/Games/Monsters%20Academy%201/js/plugins/YEP_X_BattleSysATB.js:797)
at Function.BattleManager.updateATBTicks (/C:/Users/Joshya/Documents/Games/Monsters%20Academy%201/js/plugins/YEP_X_BattleSysATB.js:991)
at Function.BattleManager.updateATBPhase (/C:/Users/Joshya/Documents/Games/Monsters%20Academy%201/js/plugins/YEP_X_BattleSysATB.js:985)
at Function.BattleManager.update (/C:/Users/Joshya/Documents/Games/Monsters%20Academy%201/js/plugins/YEP_X_BattleSysATB.js:951)
at Scene_Battle.updateBattleProcess (rpg_scenes.js:2050)
at Scene_Battle.update (rpg_scenes.js:2042)
at Scene_Battle.update (/C:/Users/Joshya/Documents/Games/Monsters%20Academy%201/js/plugins/YEP_VictoryAftermath.js:695)
at Function.SceneManager.updateScene (rpg_managers.js:1673)
at Function.SceneManager.updateMain (rpg_managers.js:1641)
at Function.SceneManager.update (rpg_managers.js:1576)