I had bit different problem in player character blueprint.
After very long looking for cause of jittering i found out that i was updating direction of character and thus fighting with build in character movement component.
Character then was locally rotated (by underlying character C++ code) then server rotated its instance on server and replicated back. That caused concurrent updates to direction.
However from your code i see you probably do not have this (above) case.
There is also another possible cause of jittering that i know.
If you overwrite rotation of character, and you have set character component properties to face movement direction, then you have concurrent updates.
This stuff is invisible in local game, because both updates happen in same tick and most recent wins.
But on remote game, winner (most recent update) is replicated back to local client. And you have jittering.
Look carefully if jittering strength depends on direction of movement. If there is some direction without jittering then opposite direction has it very bad.
You most probably have some property turned on that rotates character to movement direction or to controller rotation.
Check those property’s of character movement component.
Ps. ther is also trick that can smooth camera jittering: add camera arm with a bit of lag.