When a morph is too agressive, that can happen if the part below it does not follow....
Things like that can best be looked at and checked in wireframe mode.
Then you see what happens... and what needs to be done.

Poser 1, 2, 3, 4, 5, 7, P8 and PPro2010, P9 and PP2012, P10 and PP2014 Game Dev
"Do not drive faster then your angel can fly"!