I rather think the moment is the isuue, but you're one of them (Force or Moment) seems to be not correct. The shared edges of top flange and the vertical faces (which are also bonded to the rear plate) are a potential problem. Do you have an idea how to check if that's an isue? So only investigation in that direction is as follows: I also created a case 2 (see fig. 1 right side). Here, the vertical faces are not bonded at all. So in case 2 there are no shared edges of the contact faces. I haven't posted the results for case 2. But it's the same issue. Superposition of bending stress and tensile stress leads to too high stresses sig_y,max at the top edge. That's why I think the shared edge are might not be the problem. But still, it would be worth analyzing this topic.Â