You don’t set Rep_notify variables in the OnRep function.
Server pickup
Is currently holding, do some stuff → Set rep_notify variable
On rep function: Branch (rep_not var): true → do this, False → do something else.
Think of the on rep var as a switch/toggle. When the server changes the value of the var (toggles it) the on rep function is executed. Based on the toggled value you do A or B.
Another key factor when using Rep_notify on actors is you should use a pretty high net cull distance. It should be higher than the actors render cull distance. This ensures that any changes occur prior to the player being able to see them.
For instance If I drop an actor w/physics it should be on the ground well before an approaching “out of range” player gets close enough to see it floating.