Thanks Robert, that already helps a lot. Glad to know it is a non-trivial question.
We are actually trying to cross-check some analytical solutions, so I would like to get this to work at least to some degree of confidence.
I've tried swapping out a simple neohookean system with bulk penalty and all that like in the example. A warp violation seems to be causing an exception after one iteration with a nominal amount of stress.
I've been digging through the nonlinear solver's parameters and can't find a way to shrink the initial step size. The other work-around I can think of is to use a time stepper to gradually increase the stress. Is there another/easier way to do this?
Also, is it normal for a system with a fairly large deformation to throw a warp violation and then still recover afterwards (if so, then maybe this exception is a bug?)