Multiplayer does not like physics.
You can make them all jump and use physics only clientside
Then on event tick you tell server locations, and replicate them without actually doing physics replication server side.
So only local player on local machine has physics, then it tells server its location and server replicates that without physics.
However I am not sure if this will work.
Also for seeking better advice i would suggest joining unreal slackers chat on slack, there are some people that may actually help.