weird axis velocity/pressure
 

I am trying to validate an EHD Solver based on Interfoam I created.
For that I want to simulate the deformation of a droplet which is stressed by an electric field.

However the simulation is resulting in what is best described as a weird standing wave between the droplet and electrodes, which points perpendicular to the axis and radial direction. This velocity switches from negative to positive everry cell along the axis. The pressure is below 0 in these "standing waves"

While I first thought it might be a result of the added Maxwell term to the Velocity equation, there is no correlation to be found. I assume it is some kind of numerical oscillation, but dont know where it is coming from.

Test Case and solver can be found here:
https://www.dropbox.com/scl/fi/fhjoj...2vsi2ltgj&dl=0