Contact

In my opion something si moving. Run a very corse mesh with draft elements, use the FFE solver and show the convergence plot. IF it is not running nicely down hill it is typically a good indication that something is moving.

I would attached an elastic support to every part or ones that you may have a suspicion may have unrestricted DOF's. Just use some low stiffness relative to the problem. This will get you a solution eventually and then you can see what is moving. Remember if things are not strictly conincident they will not get the default bonded connection or whatever is specificed as the default if not a bonded.

Alternatively, you can set the default to free and manually apply all contacts pretty easily usig the select contacts option.

In my experience, this does not look like a software issue but a restraint issue. FEA is a stiffness based method so things need tohave some stiffness or things don't converge very quickly or not at all.

Also in the solver options check the apply soft springs and this, while a bit slow, will usually get you an answer so you can see what is moving.

Also the contact iterations are not vectorized so you would see low CPU utilization if it is spending a lot of time on the contacts. The solvers are vectorized for the stiffness matrix inversion.

Good luck.