I am running a study on a rear upright. The geometry of the rear is almost identical to that of the front, assembly-wise. The only difference would be the geometry of the model, more external loads, and only one more model included in the simulation. I had little to no difficulty running the study on the front assembly, but I am having a lot of difficulty doing the same for the rear. The solution times are either much higher(when the simulation is successful) or the study does not finish entirely. I cannot understand why. There is little to no difference in the contact restraints, loads, and fixtures applied to the model. In fact, I am using a coarse mesh to try and reduce solution times, and this assembly has less than half the number of elements/degrees of freedom than the front assembly but much higher solution times! I have also carried my study from the ground up, adding components and making changes little by little to isolate what the issue might be. The only issue I found was using bolted connections. I have a no pentration component contact between the two faces that are bolted together, yet I still get a prompt informing me that "contact restraints are not defined between bolted connectors". I manually implemented conact sets rather than a component contact (running out of ideas), and the simulation failed. I then used real bolts, no penetration component contact, and received a prompt saying "iteration stopped, model may have inadequate fixtures". Not making sense to me, and I'm running out of ideas...
Any thoughts about why this might happening?