Custom monster issue!

[xxxxxxxxxxxxxxxx]

Here's some stuff you can try in Maya prior to exporting the .dae to figure out where the problem lies:

1. Delete the history - often a surprisingly easy fix for all sorts of things: Select your mesh, then go to Edit> delete by Type> non-deformer history. note that "delete non-deformer history" will leave your skinning intact while "delete history" will also delete your skinning!

2. Re-do the skinning. I think I heard somewhere that hpl has problems if there are too many joints influencing one vertex and your exploded mesh looks a lot like a skinning problem. Use delete history to clean the old skinning, then select your mesh and the highest joint in your hierarchy go to Skin> Smooth bind (select the "Animation" menu from the dropdown first or you may not find it). Make sure you click the little square, not the word, this will bring up options. Bind to joint hierarchy, skinning method is classic linear, set normalize weights to interactive and most importantly, set max infulences to 2. (3 works too I think...but try 2 just to be safe.)

Of course if it turns out this really was the cause of the problem, you'll have to redo your weight painting. So try if the export works before you start painting the weights! ^^

3. Make a mesh cleanup. This will show you errors in your mesh like non-manifold geometry, n-gons... all those "rat's nests" that might be hiding in there, causing problems. Select your mesh, then go to mesh> Cleanup. Make sure you have "select matching polygons" selected, not "cleanup matching polygons", otherwise Maya will try to do stuff on it's own with unpredictable results! Then tick the boxes for everything you want Maya to search for and click apply.

Hm... if I get more ideas I'll write again. Good luck!