That is likely due to the new changes: New Player and Character Destroy Behavior Enabled by Default
In your niche case, you can disable this behavior, however, ensure you are practicing good coding habits by disconnecting connections attached to the Player and all of it’s character lifetime. This property, however, might be permanently enabled “in Q1 2025”, so I would recommend finding another solution by then via cloning (using something like CharacterRemoving will ensure your Character will still be available to clone) or using a different approach of assigning characters.