[VX] method error in Tankentai atb 1.2c

[Geokoer]

Hello you wizards out there,
During my latest test battle (in-game) against a new enemy, I usually get a method error around halfway of the battle. It refers to the ATB 1.2c script for Tankentai SBS. The error is about the following line:[spoiler]  @base_act_count = base *  100 / act_type[1][/spoiler]

The whole section the line is part from:[spoiler]def change_act(act_type)
    change_atb
    case act_type[0]
    when 0
      base = @battler.at_speed * @battler.agi
      base = @battler.at_speed * @battler.agi / act_type[2] if act_type[2] != 0
    when 1
      base = @battler.at_speed * @battler.agi / @battler.speed_level
    when 2
      base = @battler.at_speed * @battler.agi if @battler.low_speed_level == 0
      base = @battler.at_speed * @battler.agi / @battler.low_speed_level
    when 3
      base = @battler.at_speed * @battler.agi if @battler.speed_level / 2 + @battler.low_speed_level / 2 == 0
      base = @battler.at_speed * @battler.agi / (@battler.speed_level / 2 + @battler.low_speed_level / 2)
    when 4
      base = @battler.at_speed
    end
    if act_type[1] <= 0
      @base_act_count = 1000
    else
      @base_act_count = base *  100 / act_type[1]
    end
    @base_act_count = 1 if @base_act_count == 0
    @battler.act_count = 0
    @gauge.bitmap = Cache.system("act_bar")
    @battler.atb_count_up = false
    @battler.at_active = false
  end[/spoiler]

This is the first time it happens. The only new addition to this battle (apart from new enemy skills etc) is that one temporary teammate is added that auto-battles.

Can anyone help me out why this error persists, and explain to me how I can get rid of it?

Much obliged,
~ Geoff

[Geokoer]

Problem update: Seems it had to do with one of the skills the aut-character used. Removing it seems to have done the trick.

I do wonder about that though. The skill would give the whole tea + defense; why would that not work?