There are multiple functionalities that have issues when playing online on a server.
Here are some of them, and issues related to them:
The audio test ball does not appear for other players in a server. All the sounds that are played therefore, do not play for other players. This issue does not occur with a firearm implementation in “GunTesting” server, where the sounds made by the gun were heard by all the players present.

Gravity effects do not work on other players, but they do work on the NPCs, and other objects which are affected by gravity.

Current implementation of the fog does not transfer to other players, it strictly affects only the player who changed the fog settings:


The same applies to the Scene Lights, it is visible only to the player who changed the settings:

If the player did change some settings, for example, in the Sky & Lighting, changes to which are visible for all the players, the act of disconnecting and joining back again, causes the default settings to apply for the rejoined player, while the rest of the server has the modified settings applied and visible to everyone who was present in the server at the time of changing the settings.
Default Sky & Lighting settings:
