I have the same problem as Marco had.
I need to do the thermal check and show that isothermal expansion show no stresses. I did a simple example shown in the picture attached. I used a shell plate and connected the plate to a beam with RBE2 elements. I turned on the LAGRANGE mode in Rigid case control and in the displacement post-processing it looks like everything is expanding consistently. But then the von-mises stresses show quite high stresses at the elements connected to RBE2 nodes.
Do you know if I need to change anything else in the settings in order to have no stresses during expansion?