Enemy with hitbox glitching when there is more of him

Can you make a small demo or post a screenshot of the event sheet? Your project is 27MB in size and requires addons which I don't want to install.

Remove "trigger once" from all events and never ever use it inside of triggers, loops, and especially with objects that have multiple instances! It's the cause of all your bugs.

Instead of "trigger once" use additional conditions, or Timer behavior. For example, in the last event on your first screenshot you can add another condition: Tween "Idle" is not playing.

Timer is a very useful behavior for such games. For example:

Enemy has LineOfSight to Player 
Enemy timer "attack" is not running : Enemy start timer "attack" for 1 second

Enemy On timer "attack" : Enemy spawn a bullet

It's like this?

Also, I forgot to tell, the hitbox has an hierarchy with the animation sprite, and the hitbox is the parent.

It's working slightly better, but you didn't understood. They were glitching when there were multiple instances, and I wanted to them work independently from each other. Also, they are composed of hitbox and animation sprites, and how they work is basically: When you get close to one, it reveals itself and starts chasing you. When you get closer, it jumps on your direction to attack.

Ok, I see in your screenshots that you are not picking child animator sprite. You need to add "BushMohHitbox pick children BushMohSprite" to all relevant events.

Another option is to add these two objects to hierarchy a container. Then BushMohSprite will be created automatically for every hitbox (you don't need to spawn it), but you can still add it as a child. And it will be picked automatically in all events.