The output of Simulink.B​lockDiagra​m.getIniti​alState does not include all states of multibody model

I am trying to determine the stability of a Simscape Multibody model. I'm using linmod to create a statespace model and then eig to calculate the eigenvectors and eigenvalues. linmod runs without error, but when digging into the StateName attribute of the linmod output I see that not all of the joint states are listed.

For my model with 5 Bushing joints (along with some Revolute and Spherical joints) all 12 states of one Bushing joint are shown. But the other Bushing joints only list the rotation position and rate states. All of the states for the Revolute and Spherical joints are listed.

I also used the Simulink.BlockDiagram.getInitialState function which results in the same list with the missing states.

I have confirmed with the Model Report from Mechanics Explorer that all joints and constraints are assembled.

I have also confirmed for a simple 2 spring/mass/damper model (concentrated masses joined with Cylindrical joints with stiffness and damping) the 8 states are listed in StateName (translation and rotation position and rate for two cylindrical joints).

Is there a setting or parameter that I need to set, or is there a modeling error I should look for that would cause this to happen?