I am trying to use the submodeling technique to try out various optimizations on a small part of my overall model. Unfortunately the "Displacement from parent" fixture keeps losing the faces it should be assigned to, even though I'm not changing them. See screenshots below showing the first submodel, and the duplicated simulation with the new geometry that is missing one face fixture. This would be fantastic to get working as the overall model takes upwards of a few hours to run and the sub model takes about 5 minutes!

What am I doing wrong?