Program: 22392
Project: 22392
Buggy source:
@SubscribeEvent public void onPlayerTick(TickEvent.PlayerTickEvent event){
  EntityPlayer player=event.player;
  World world=player.worldObj;
  boolean isServer=event.side == Side.SERVER;
  ItemStack chest=player.getCurrentArmor(2);
  ItemStack boots=player.getCurrentArmor(0);
  if (!isServer) {
    this.isJumping=Minecraft.getMinecraft().gameSettings.keyBindJump.getIsKeyPressed();
  }
  ticksSinceLastCellFill++;
  if (BaublesIntegration.checkForSteamCellFiller(player)) {
    if (ticksSinceLastCellFill >= 10) {
      for (int i=0; i < InventoryPlayer.getHotbarSize(); i++) {
        ItemStack item=player.inventory.getStackInSlot(i);
        if (item != null && item.getItem() instanceof ItemSteamCell && ItemSteamCell.chargeItems(player,false)) {
          player.inventory.decrStackSize(i,1);
          ticksSinceLastCellFill=0;
          break;
        }
      }
    }
  }
 else {
    ticksSinceLastCellFill=-40;
  }
  if (isJumping) {
    if (boots != null && boots.getItem() instanceof ItemExosuitArmor) {
      ItemExosuitArmor item=(ItemExosuitArmor)boots.getItem();
      if (item.hasUpgrade(boots,SteamcraftItems.doubleJump) && SteamcraftEventHandler.hasPower(player,15)) {
        if (isServer) {
          if (!boots.stackTagCompound.hasKey("String_Node_Str")) {
            boots.stackTagCompound.setBoolean("String_Node_Str",false);
          }
          if (!boots.stackTagCompound.hasKey("String_Node_Str")) {
            boots.stackTagCompound.setBoolean("String_Node_Str",false);
          }
        }
        if (!player.onGround && boots.stackTagCompound.getBoolean("String_Node_Str") && !boots.stackTagCompound.getBoolean("String_Node_Str")&& !player.capabilities.isFlying) {
          if (isServer) {
            boots.stackTagCompound.setBoolean("String_Node_Str",true);
            SteamcraftEventHandler.drainSteam(player.getCurrentArmor(2),10);
          }
          player.motionY=0.65D;
          player.fallDistance=0.0F;
        }
        if (isServer) {
          boots.stackTagCompound.setBoolean("String_Node_Str",false);
        }
      }
    }
    if (chest != null && chest.getItem() instanceof ItemExosuitArmor) {
      ItemExosuitArmor item=(ItemExosuitArmor)chest.getItem();
      if (item.hasUpgrade(chest,SteamcraftItems.jetpack) && SteamcraftEventHandler.hasPower(player,5)) {
        if (!player.onGround && !player.capabilities.isFlying) {
          player.motionY+=0.06D;
          player.fallDistance=0.0F;
          if (!isServer) {
            double rotation=Math.toRadians(player.renderYawOffset);
            world.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);
            world.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 {
            SteamcraftEventHandler.drainSteam(chest,Config.jetpackConsumption);
          }
        }
      }
      if (item.hasUpgrade(chest,SteamcraftItems.pitonDeployer) && isServer) {
        if (chest.stackTagCompound.hasKey("String_Node_Str") && chest.stackTagCompound.getBoolean("String_Node_Str")) {
          chest.stackTagCompound.setBoolean("String_Node_Str",false);
        }
      }
    }
  }
 else {
    if (boots != null && boots.getItem() instanceof ItemExosuitArmor) {
      ItemExosuitArmor item=(ItemExosuitArmor)boots.getItem();
      if (item.hasUpgrade(boots,SteamcraftItems.doubleJump) && !player.onGround && isServer) {
        boots.stackTagCompound.setBoolean("String_Node_Str",true);
      }
    }
  }
}

Fixed version (ground truth):
@SubscribeEvent public void onPlayerTick(TickEvent.PlayerTickEvent event){
  EntityPlayer player=event.player;
  World world=player.worldObj;
  boolean isServer=event.side == Side.SERVER;
  ItemStack chest=player.getCurrentArmor(2);
  ItemStack boots=player.getCurrentArmor(0);
  if (!isServer) {
    this.isJumping=Minecraft.getMinecraft().gameSettings.keyBindJump.getIsKeyPressed();
  }
  if (CrossMod.BAUBLES) {
    ticksSinceLastCellFill++;
    if (BaublesIntegration.checkForSteamCellFiller(player)) {
      if (ticksSinceLastCellFill >= 10) {
        for (int i=0; i < InventoryPlayer.getHotbarSize(); i++) {
          ItemStack item=player.inventory.getStackInSlot(i);
          if (item != null && item.getItem() instanceof ItemSteamCell && ItemSteamCell.chargeItems(player,false)) {
            player.inventory.decrStackSize(i,1);
            ticksSinceLastCellFill=0;
            break;
          }
        }
      }
    }
 else {
      ticksSinceLastCellFill=-40;
    }
  }
  if (isJumping) {
    if (boots != null && boots.getItem() instanceof ItemExosuitArmor) {
      ItemExosuitArmor item=(ItemExosuitArmor)boots.getItem();
      if (item.hasUpgrade(boots,SteamcraftItems.doubleJump) && SteamcraftEventHandler.hasPower(player,15)) {
        if (isServer) {
          if (!boots.stackTagCompound.hasKey("String_Node_Str")) {
            boots.stackTagCompound.setBoolean("String_Node_Str",false);
          }
          if (!boots.stackTagCompound.hasKey("String_Node_Str")) {
            boots.stackTagCompound.setBoolean("String_Node_Str",false);
          }
        }
        if (!player.onGround && boots.stackTagCompound.getBoolean("String_Node_Str") && !boots.stackTagCompound.getBoolean("String_Node_Str")&& !player.capabilities.isFlying) {
          if (isServer) {
            boots.stackTagCompound.setBoolean("String_Node_Str",true);
            SteamcraftEventHandler.drainSteam(player.getCurrentArmor(2),10);
          }
          player.motionY=0.65D;
          player.fallDistance=0.0F;
        }
        if (isServer) {
          boots.stackTagCompound.setBoolean("String_Node_Str",false);
        }
      }
    }
    if (chest != null && chest.getItem() instanceof ItemExosuitArmor) {
      ItemExosuitArmor item=(ItemExosuitArmor)chest.getItem();
      if (item.hasUpgrade(chest,SteamcraftItems.jetpack) && SteamcraftEventHandler.hasPower(player,5)) {
        if (!player.onGround && !player.capabilities.isFlying) {
          player.motionY+=0.06D;
          player.fallDistance=0.0F;
          if (!isServer) {
            double rotation=Math.toRadians(player.renderYawOffset);
            world.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);
            world.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 {
            SteamcraftEventHandler.drainSteam(chest,Config.jetpackConsumption);
          }
        }
      }
      if (item.hasUpgrade(chest,SteamcraftItems.pitonDeployer) && isServer) {
        if (chest.stackTagCompound.hasKey("String_Node_Str") && chest.stackTagCompound.getBoolean("String_Node_Str")) {
          chest.stackTagCompound.setBoolean("String_Node_Str",false);
        }
      }
    }
  }
 else {
    if (boots != null && boots.getItem() instanceof ItemExosuitArmor) {
      ItemExosuitArmor item=(ItemExosuitArmor)boots.getItem();
      if (item.hasUpgrade(boots,SteamcraftItems.doubleJump) && !player.onGround && isServer) {
        boots.stackTagCompound.setBoolean("String_Node_Str",true);
      }
    }
  }
}