Odd Force Output Implicit Analysis

I stumbled upon an unexpected behaviour regarding the force output in an implicit analysis.

I look at the following model of a honeycomb unit cell. On both ends there is a RBODY. While at the top there is an imposed velocity and the bottom is fixed in all 6 dof. The top RBODY is additionally constrained so that the downward movement is guided. (in case you are wondering, the nodes of the model are randomly distorted in order to achieve buckling also in implicit analysis)

I have been playing around with implicit and explicit solvers. Using the explicit solver I get very much an expected behavior of the force. I plotted both the SPC reaction force in Z (direction of IMPVEL) and the FZ of the RBODY at the top.
Both are more or less the same and it machtes my experiments.

However when I do implicit analysis i get odd results. First of all the FZ of the upper RBODY and the REACZ of the lower SPC are not the same. Secondly and most importantly, the force does not start at zero, which completely doesnt make sense.

When I do Non-Linear implicit I manage to get to initial force almost to zero, depending on what initial time step I set. The smaller the initial time step, the closer I get to ZeroForce at start.

However, the forces of the upper RBODY and the lower SPC are not the same. The force of the RBODY seems to match the explicit analysis. The SPC Force seems to be wrong.

Can anybody explain this to me? What do I do wrong? I have attached two picture (of the Model and of the plot) as well as the model files.

Regards
Ralf