material assignment issue

I am trying to assign material to Bentley Architecture forms. Everytime I reopen the design file, the assignment is lost. I have to reassign it. I noticed some walls don't remember material assignment and some do. This doesn't happen when I attach material in 3D surface/face or even object like solids/mesh. These objects remember the material. Does anyone knows why exactly this happens? Any thoughts would be of great help. I am using the MicroStation 08.11.07.27 with Luxology 24a. BA is the 08.11.07.26 I guess.