After further testing on another machine I can say that the bug is definitely related to tweaks SM made to Poser's default skinning method.

It goes away when the figure is switched to the new Unimesh skinning.

BUT, this of course is still no solution as the new Unimesh skinning method breaks ColorCurvators PoseMorphLoader, which I almost use on a daily basis.

(See screenshot).

And if it breaks that, who knows what other essential tools the new skinning might break, too.

The new skinning also changes the mesh appearance slightly, and doesn't work for all older meshes.

It's great to have an alternative skinning method which allows subdivision, but this doesn't mean the old skinning method can be effectively made unuseable.

It needs to be fully functional, especially given the fact that a lot of people still use older figures in lack of a viable set of new figures.