Current Behavior: If a character is badly wounded and shifts from a high Constitution form to a lower Constitution form (even if it's his natural form), he will instantly die, assuming that the HP lost from the difference in Constitution score was greater than the character's remaining HP. A character that dies this way also doesn't drop any equipment on the ground, though a Raise Dead spell will resurrect them with all their equipment intact anyway.
Expected Behavior: Shapeshifting from a high to low Constitution form doesn't outright kill you, but leaves you with the same remaining HP as before.
On a side related note. The Flind form is still not proficient with its own halberd.