Hi Makis,
thanks for the prompt reply.
The interface is just a wall patch with moving wall velocity (U), zeroGradient for pressure and fixed value in fixedValue in pointDisplacement.
Honestly, there is nothing special with this point. This is even not the centre point of the geometry (not 0/0/0).
I ran in serial. I can share this case if you are interested.
Best regards
Ulrich