Setup
Create a simple mission with Zeus, and create a 3den Composition of a group of 4.
Use CBA to allow the use of target watch tables and target execution.
Run the mission on a dedicated server (can be locally hosted).

Checking waypoints
Place down the composition, check the waypoints of the group by looking at the leader and putting this in a local watch list:

waypoints group cursorObject;

This results into: [[B Alpha 1-2,0]].
Create a global object variable with:

cursorObject call BIS_fnc_objectVar;

Now check the waypoints of the group on another machine (IE. the server) with (use CBA to enable target watch tables):

waypoints group bis_o4_27; // -- Use var generated by BIS_fnc_objectVar

This results into: [].
Meaning that the waypoints aren't properly synced.

Giving waypoints
When giving an waypoint from another machine the group ignores it.
Try this by running the folowing on the server:

(group bis_o4_27) addWaypoint [(bis_o4_27 getPos [50, 0]), -1]; // -- Adds waypoint 50 meters ahead

You should see the waypoint added locally and on the target. However the group won't move.
You first have to clear the waypoints where the group was created, to allow them to be controlled by another machine.
Eg. with:

for "_i" from ((count waypoints (group bis_o4_27 )) - 1) to 0 step -1 do 
{ 
       deleteWaypoint [(group bis_o4_27 ), _i]; 
};

When using this with headless-clients this causes issues where zeuses can't control the AI, because locally they have a waypoint but according to anyone else they don't.
Causing the AI to ignore any other waypoints.

More steps to reproduce can be given if required.
Including a mission file.