Multiplayer variable replication: Client "Accessed none"?

I am learning the basics of UE4 networking and preparing my game for multiplayer:

A character has a variable “healthbarMaterial” (Type: Dynamic MaterialInstance).
The Material is set to an Instance of a Material i created on the construction event.

Running the level on serverside works fine, on a client somehow my variable is not synced.
"healthbarMaterial is set to “replicate”. I am pretty sure i missed some pretty basic stuff here.

The following error occurs in the Message Log:

ConstructionEvent of Actor Z_Unit:

This is the corresponding function “HandleHealthbar”:

Settings for variable “HealthbarMaterial”:

You don’t need to replicate anything graphics related, client should handle that based on game data he have from gameplay replication. I kind of susspecting server actully replicates none due fact it does not run rendering if you do dedicated, thats why you got errors

It is not dedicated, i run two windows, one client and one server.

Changing the material to be applied on both, server and client without replicating fixet it.
But somehow that does not fix the fact, that the replication for Dynamic Material Instances is somehow broken?

Otherwise if UE4 does not support replicating Material Instances, it should say that in it’s documentation.