Applying line displacement to a beam

Hello,

I want to apply a uniform "10mm displacement to the right" to the embedded beam below (the purple vertical line between nodes 1 and 2). However PlAXIS tells me that this is not allowed as the line is already assigned to a beam and cant be assigned to a line displacement as well.

Other things I have tried: 

1. Adding two point displacement to only node 1 and node 2 => this works but the displacement in the middle of the beam wont be exactly 10mm as the displacement is not applied uniformly in the entire beam.

2. Adding a couple more point displacements in the middle of the beam (between point 1 and point 2) => for some reason the model fails before even applying the displacements and I dont know why?

Is there anything I can do about this?

Cheers