Program: 22495
Project: 22495
Buggy source:
@SubscribeEvent @SideOnly(Side.CLIENT) public void tickStart(TickEvent.ClientTickEvent event){
  wasInUse=inUse;
  inUse=false;
  if (event.side == Side.CLIENT && Minecraft.getMinecraft().thePlayer != null) {
    EntityPlayer player=Minecraft.getMinecraft().thePlayer;
    if (SteamcraftEventHandler.hasPower(player,1) && player.getEquipmentInSlot(2) != null && player.getEquipmentInSlot(1).getItem() instanceof ItemExosuitArmor) {
      ItemExosuitArmor chest=(ItemExosuitArmor)player.getEquipmentInSlot(2).getItem();
      if (player.worldObj.isRemote && chest.hasUpgrade(player.getEquipmentInSlot(2),SteamcraftItems.thrusters)) {
        if (!player.onGround && Math.abs(player.motionX) + Math.abs(player.motionZ) > 0.0F && !player.isInWater() && !(player.capabilities.isFlying)) {
          double rotation=Math.toRadians(player.renderYawOffset + 90.0F);
          double rotation2=Math.toRadians(player.renderYawOffset + 270.0F);
          player.worldObj.spawnParticle("String_Node_Str",player.posX + 0.5 * Math.sin(rotation),player.posY - 1F,player.posZ - 0.5 * Math.cos(rotation),player.motionX * -0.1F,0,player.motionZ * -0.1F);
          player.worldObj.spawnParticle("String_Node_Str",player.posX + 0.5 * Math.sin(rotation2),player.posY - 1F,player.posZ - 0.5 * Math.cos(rotation2),player.motionX * -0.1F,0,player.motionZ * -0.1F);
        }
      }
    }
    if (Minecraft.getMinecraft().gameSettings.keyBindJump.getIsKeyPressed()) {
      SteamcraftClientPacketHandler.sendSpacePacket(player);
      if (player != null) {
        ItemStack armor=player.getCurrentArmor(2);
        if (armor != null && armor.getItem() == SteamcraftItems.exoArmorBody) {
          ItemExosuitArmor item=(ItemExosuitArmor)armor.getItem();
          if (item.hasUpgrade(armor,SteamcraftItems.jetpack) && SteamcraftEventHandler.hasPower(player,5)) {
            if (!player.onGround && !player.capabilities.isFlying) {
              player.motionY=player.motionY + 0.06D;
              double rotation=Math.toRadians(player.renderYawOffset);
              player.worldObj.spawnParticle("String_Node_Str",player.posX + 0.4 * Math.sin(rotation + 0.9F),player.posY - 1F,player.posZ - 0.4 * Math.cos(rotation + 0.9F),0.0F,-1.0F,0.0F);
              player.worldObj.spawnParticle("String_Node_Str",player.posX + 0.4 * Math.sin(rotation - 0.9F),player.posY - 1F,player.posZ - 0.4 * Math.cos(rotation - 0.9F),0.0F,-1.0F,0.0F);
            }
          }
        }
      }
    }
 else {
    }
    ItemStack item=player.inventory.getStackInSlot(player.inventory.currentItem);
    if (item != null && item.getItem() == SteamcraftItems.spyglass) {
      if (Minecraft.getMinecraft().gameSettings.thirdPersonView == 0) {
        inUse=true;
        this.renderTelescopeOverlay();
      }
    }
    if (!wasInUse && item != null && item.getItem() == SteamcraftItems.musket && UtilEnhancements.getEnhancementFromItem(item) == SteamcraftItems.spyglass) {
      boolean isShooting=false;
      if (item.stackTagCompound != null) {
        NBTTagCompound nbt=item.getTagCompound();
        if (nbt.getInteger("String_Node_Str") > 0) {
          isShooting=true;
        }
      }
      if (isShooting && Minecraft.getMinecraft().gameSettings.thirdPersonView == 0) {
        inUse=true;
        Minecraft.getMinecraft().gameSettings.fovSetting=-0.85F;
        Minecraft.getMinecraft().gameSettings.mouseSensitivity-=0.3F;
        this.renderTelescopeOverlay();
      }
    }
  }
  if (!inUse && !wasInUse) {
    fov=Minecraft.getMinecraft().gameSettings.fovSetting;
    sensitivity=Minecraft.getMinecraft().gameSettings.mouseSensitivity;
  }
  if (!inUse && wasInUse) {
    Minecraft.getMinecraft().gameSettings.fovSetting=fov;
    Minecraft.getMinecraft().gameSettings.mouseSensitivity=sensitivity;
  }
  if (inUse && !wasInUse) {
    this.zoom=0.0F;
  }
  if (inUse && Minecraft.getMinecraft().gameSettings.keyBindAttack.getIsKeyPressed() && zoom > 0F) {
    this.zoom-=1.0F;
    Minecraft.getMinecraft().gameSettings.fovSetting+=0.05F;
    Minecraft.getMinecraft().gameSettings.mouseSensitivity+=0.01F;
  }
  if (inUse && Minecraft.getMinecraft().gameSettings.keyBindUseItem.getIsKeyPressed() && zoom < 34F) {
    this.zoom+=1.0F;
    Minecraft.getMinecraft().gameSettings.fovSetting-=0.05F;
    Minecraft.getMinecraft().gameSettings.mouseSensitivity-=0.01F;
  }
}

Fixed version (ground truth):
@SubscribeEvent @SideOnly(Side.CLIENT) public void tickStart(TickEvent.ClientTickEvent event){
  wasInUse=inUse;
  inUse=false;
  if (event.side == Side.CLIENT && Minecraft.getMinecraft().thePlayer != null) {
    EntityPlayer player=Minecraft.getMinecraft().thePlayer;
    if (SteamcraftEventHandler.hasPower(player,1) && player.getEquipmentInSlot(2) != null && player.getEquipmentInSlot(2).getItem() instanceof ItemExosuitArmor) {
      ItemExosuitArmor chest=(ItemExosuitArmor)player.getEquipmentInSlot(2).getItem();
      if (player.worldObj.isRemote && chest.hasUpgrade(player.getEquipmentInSlot(2),SteamcraftItems.thrusters)) {
        if (!player.onGround && Math.abs(player.motionX) + Math.abs(player.motionZ) > 0.0F && !player.isInWater() && !(player.capabilities.isFlying)) {
          double rotation=Math.toRadians(player.renderYawOffset + 90.0F);
          double rotation2=Math.toRadians(player.renderYawOffset + 270.0F);
          player.worldObj.spawnParticle("String_Node_Str",player.posX + 0.5 * Math.sin(rotation),player.posY - 1F,player.posZ - 0.5 * Math.cos(rotation),player.motionX * -0.1F,0,player.motionZ * -0.1F);
          player.worldObj.spawnParticle("String_Node_Str",player.posX + 0.5 * Math.sin(rotation2),player.posY - 1F,player.posZ - 0.5 * Math.cos(rotation2),player.motionX * -0.1F,0,player.motionZ * -0.1F);
        }
      }
    }
    if (Minecraft.getMinecraft().gameSettings.keyBindJump.getIsKeyPressed()) {
      SteamcraftClientPacketHandler.sendSpacePacket(player);
      if (player != null) {
        ItemStack armor=player.getCurrentArmor(2);
        if (armor != null && armor.getItem() == SteamcraftItems.exoArmorBody) {
          ItemExosuitArmor item=(ItemExosuitArmor)armor.getItem();
          if (item.hasUpgrade(armor,SteamcraftItems.jetpack) && SteamcraftEventHandler.hasPower(player,5)) {
            if (!player.onGround && !player.capabilities.isFlying) {
              player.motionY=player.motionY + 0.06D;
              double rotation=Math.toRadians(player.renderYawOffset);
              player.worldObj.spawnParticle("String_Node_Str",player.posX + 0.4 * Math.sin(rotation + 0.9F),player.posY - 1F,player.posZ - 0.4 * Math.cos(rotation + 0.9F),0.0F,-1.0F,0.0F);
              player.worldObj.spawnParticle("String_Node_Str",player.posX + 0.4 * Math.sin(rotation - 0.9F),player.posY - 1F,player.posZ - 0.4 * Math.cos(rotation - 0.9F),0.0F,-1.0F,0.0F);
            }
          }
        }
      }
    }
 else {
    }
    ItemStack item=player.inventory.getStackInSlot(player.inventory.currentItem);
    if (item != null && item.getItem() == SteamcraftItems.spyglass) {
      if (Minecraft.getMinecraft().gameSettings.thirdPersonView == 0) {
        inUse=true;
        this.renderTelescopeOverlay();
      }
    }
    if (!wasInUse && item != null && item.getItem() == SteamcraftItems.musket && UtilEnhancements.getEnhancementFromItem(item) == SteamcraftItems.spyglass) {
      boolean isShooting=false;
      if (item.stackTagCompound != null) {
        NBTTagCompound nbt=item.getTagCompound();
        if (nbt.getInteger("String_Node_Str") > 0) {
          isShooting=true;
        }
      }
      if (isShooting && Minecraft.getMinecraft().gameSettings.thirdPersonView == 0) {
        inUse=true;
        Minecraft.getMinecraft().gameSettings.fovSetting=-0.85F;
        Minecraft.getMinecraft().gameSettings.mouseSensitivity-=0.3F;
        this.renderTelescopeOverlay();
      }
    }
  }
  if (!inUse && !wasInUse) {
    fov=Minecraft.getMinecraft().gameSettings.fovSetting;
    sensitivity=Minecraft.getMinecraft().gameSettings.mouseSensitivity;
  }
  if (!inUse && wasInUse) {
    Minecraft.getMinecraft().gameSettings.fovSetting=fov;
    Minecraft.getMinecraft().gameSettings.mouseSensitivity=sensitivity;
  }
  if (inUse && !wasInUse) {
    this.zoom=0.0F;
  }
  if (inUse && Minecraft.getMinecraft().gameSettings.keyBindAttack.getIsKeyPressed() && zoom > 0F) {
    this.zoom-=1.0F;
    Minecraft.getMinecraft().gameSettings.fovSetting+=0.05F;
    Minecraft.getMinecraft().gameSettings.mouseSensitivity+=0.01F;
  }
  if (inUse && Minecraft.getMinecraft().gameSettings.keyBindUseItem.getIsKeyPressed() && zoom < 34F) {
    this.zoom+=1.0F;
    Minecraft.getMinecraft().gameSettings.fovSetting-=0.05F;
    Minecraft.getMinecraft().gameSettings.mouseSensitivity-=0.01F;
  }
}