Preexisting Entities not existing on client with server having large uptime.

I have marked this as security since it seems that it could be vulnerable to exploitation to gain an unfair advantage on public servers. On my private server that I have been playing on with my friends, we have run into a very strange bug: Entities do not seem to exist on the client, unless they are newly spawned or created. This does not include particles, entities' sounds, or fire overlays, but they are unable to be targeted. In the attached screenshot, there is a Zombified Piglin wandering around, but is not rendering. Notably, it can clearly be heard and F3+B hitbox rendering is turned on, as can be faintly seen in the blaze in the top right (however it is mostly obscured by the fire from an unfortunate fireball.)