Validation of oedometer test

Hello,

My problem concerns the validation of oedometer tests.
I run some incremental loading oedometer tests on medium stiff clays and simulated them in Plaxis using different soil models (SSC, hardening soil, MCC).
I followed the procedure explained at page 192 of the Material Models Manual and considered a point on the top.
The final compression curve (stress - void ratio) matches quite well with the laboratory curve, but the entire simulated curve is shifted downwards.
The first load step, when simulated in Plaxis, returns much higher deformation than the laboratory results.
Modifying the soil model or the stiffness values or the preconsolidation stress does not solve the problem.
Another publication shows the same offset of the compression curve (Asad, 2016, Prediction of One-Dimensional Compression Test using Finite Elements Model).

I wander why this happens. 

Thanks