Object reference disappears randomly after keyframe

I'm designing a roguelite with various cards/attacks like Slay the Spire or One Step from Eden. Randomly when I use an attack, the reference to the player disappears. Specifically after a Keyframe Animation event.

I have several important scripts and objects.

   - Player (object and script)
       Stores information like player health, attack buffs
   - AttackData (script)
       Stores information about the different cards like mana cost or how much damage they deal.
   - AttackAnim (object and script)
       Created by AttackData to check if an Enemy is in range. Sends Enemy to AttackData to deal 
       damage.

1) When Player (object and script) is created, Player (script) passes itself to Attack Data to let it know the Player's current defense, health, etc.

2) When the Player attacks, AttackData picks the right card function, saves it to a variable, and then creates AttackAnim w$$anonymous$$ch is a "$$anonymous$$tbox"/spriteanimation. AttackAnim has a reference to AttackData.

3) On certain keyframes of the animation, the "$$anonymous$$tbox" becomes active.

4) If colliding with an enemy, it sends the enemies data to AttackData w$$anonymous$$ch checks the Player's strength buffs and deals damage.

I have $$anonymous$$tbox in quotes because everyt$$anonymous$$ng works on a grid so there's not colliding, instead I check if AttackAnim is occupying the same square as an Enemy,

Randomly the reference to Player in AttackData becomes null. Everyt$$anonymous$$ng breaks. Using the debugger and Debug.Log, the reference becomes null once AttackAnim's $$anonymous$$tbox becomes active at the keyframe.

I've been stuck for about a week and I'm truly at a loss.