Solved Item::setDamage() doesn't fully work

Before you give me an answer read the preamble. Thank you!

Preamble:

• I'm sure that the player is correctly handling the bow in the same inventory slot.
• I already debugged it in various ways.

That said, now I can talk about the problem!
Initially, when a player spears an arrow, the bow's durability is set to 340 using the EntityShootBowEvent.
After that, there is already in execution a repeating task that repairs the bow but here appears the problem. The durability's value doesn't change while the task tries to fix the bow.

How can I fix the problem? Thank you!

PHP:

public function onEntityShootBow(EntityShootBowEvent $event)
    {
        $entity = $event->getEntity();

        if ($entity instanceof Player) {
            $arena = $this->main->getArenaByLevel($entity->getLevel());
            if ($arena !== null) {
                if ($arena->isInArena($entity)) {
                    $bow = $event->getBow();
                    $bow->setDamage(340);
                    $entity->getInventory()->sendSlot($entity->getInventory()->getHeldItemSlot(), $entity);
                }
            }

        }
    }

PHP:

    public function onRun(int $currentTick)
    {
        foreach ($this->arena->getPlayers() as $player) {
              $bow = $player->getInventory()->getItem(1);
                if ($bow->getId() === Item::BOW) {
                    if ($bow->getDamage() > 0) {
                        if (($bow->getDamage() - 70) < 0)
                            $bow->setDamage(0);
                        else
                            $bow->setDamage(($bow->getDamage() - 70)); //TODO: I need to understand why the damage value isn't set..
                        $player->getInventory()->sendSlot(1, $player);
                    }
                }
            }
        }
    }
}

Spoiler: Debug

PluginTask started
Bow damage = 0
EntityShootBowEvent called -> Bow damage = 340
/*Task cycle*/
Bow damage > 0 ? Yes! -> Bow damage = 340 - 70 (270)
/*Another task cycle*/
What should it do:
Bow damage > 0 ? Yes! -> Bow damage = 270 - 70 (200)
What it does:
Bow damage > 0 ? Yes! -> Bow damage = 340 - 70 (270) //And it continues forever without changing damage value...

 

I didn't expect that... Thank you so much!