That's it!  Here's another recurring problem that I've had for a while, posted in hopes that someone has a solution they'd be willing to share.  After perfecting a custom morph, I zero the figure and all morphs except the new one, which I dial to 1.  I then select the relevant body part and export it as an OBJ (in the checklist that appears, I check only the "as morph target" option).  However, when I load the morph target back into a new instance of the same figure, its effect is somewhat different than the original.  It seems so random too.  The issue plagued me several months ago and then appeared to go away.  Well now, as I try to morph Vittorio's delt/pec transition so they don't seem to balloon out cartoonishly when he moves his arms down, the problem returns with a vengeance.  Here's a list of what I've tried so far:

1)   Copying the morph by setting it to 1 and choosing "spawn morph target" and then exporting the copy.

2)   Saving the one file in which the morph actually works (the one in which it was created) and then creating a binary morph INJection that uses the PMD as a basis.

Needless to say, nothing has worked.

Curiously enough, despite the apparent randomness, the one consistent aspect of the problem is that it appears most often near the collar/chest juncture on the Millenium 4 figures.

Any help will be greatly appreciated!  An operation that should take an hour is taking multiple hours because I keep having to re-morph, re-export, and hopelessly pray that it works.

You've probably checked this already, but how about the figure's scale?  If the
scale of both source and destination are not exactly 100% on BODY and all
relevant parts, the MT will be wrong. 

Or is there perhaps some FBM that is affecting the scale without showing up
as a non-100 number in an actual scale parameter?

There is some scaling involved in the overall morph of which this one is part, but I make sure to return everything to 100% before exporting.

An interesting development: the effects of the original and re-imported morph are identical in the zeroed pose but diverge when the figure (or at least any relevant body part) is posed.

This is a strange one, it sounds like you are doing everything right. "Vittorio" Is that a V4 character?
V4 has a lot of hidden magnets, and all I can think is that perhaps these are somehow implicated in the problem.

Argh!  I even tried resetting all scaling before CREATING the ORIGINAL morph.  No luck.  This wouldn't be half as infuriating if it actually MADE SENSE!

Wonder if you could use morph manager or similar to export the pose?

Have run into this problem myself from time to time and it’s also a pain to reset all poses.