You might be able to solve this by using "Families" to escape the reciprocal picking that happens with containers.
Manual > Families: https://www.scirra.com/manual/142/families Setup
Place the person into a family named "Damageable". Event
Hitbox is attacking. // Selects all attacking Hitbox objects.
For each hitbox.>> Event
Hitbox is overlapping Damageable family>>
Pseron.UID does NOT equal Damageable.UID // Prevents the Hitbox from attacking the Person who owns it.>> Actions
Damage Damageable. // Deals damage to all Persons overlapping the Hitbox who are not the Hitbox owner.
Note the sub event condition that includes Person.UID.
Here we are assuming that the Hitbox's Person is selected because they are both in the same container, and we're also hoping that won't influence the selected objects in the Damageable family, and it shouldn't, BUT...
If you want to be absolutely sure that the containers aren't involved, and thus can't get up to any of their containerly shenanigans, then instead of getting Person.UID from the Person implicitly selected along with the Hitbox, you can store the Person UID directly in the corresponding Hitbox when the Hitbox is created.Event
Hitbox, On created:Actions
Set Hitbox private variable "parentPersonUID" to Person.UID.