I encountered that problem too. The thing is that the parts that should be invisible in decay animation (all except the corpse) are not linked with a geoset animation, that should make the parts which should be invisible, invisible in that certain (decay in that case) animation.
Method to solve:
0. IMPORTANT: Convert the model into mdl file, never work in MDX file state.
1. Open the model in Magos' model editor.
2.a Go to Windows -> and click on the Geoset Manager, and put that appearing window on the left side of your screen (for more handy usage)
2.b Go to Windows -> and click on the Geoset Animation Manager, and put that appearing window on the right side of your screen
3. Go to Window -> Animation Controller, Put that window in the lower left side of you screen.
4. In Animation Controller play the Decay Bone animation and look for that model parts that are actually invisible in that animation
5. Play Unanimated or stand animation. CTRL + Lelftclick on that part that was invisible in decay aniamtion (chest, legs whatever)
6. In the geoset manager list to your left side you'll get that geoset selcted.
Don't touch the geoset manager's list !!!!
7. Go to the Geoset Animation Manager list and try to find your geoset by double clicking on a geoset animation file and checking the Geoset ID in the lower left part of that small window.
8. If you have found the right geoset, press the Alpha buttom on the right side of that window. Copy the whole block of digits by using CTRL-C (should be like:
55555: 1 (just and example)
66666: 0
whatver
9. Close the 'Alpha' window and the 'Geoset Animation' window, not the 'Geoset Animation Manager' window
10. In animation controller play again that decay animation.
11. In the main window select the parts that should be invisible in that animation.
12. Right click in the 'Geoset Animation Manager' and select 'Create New'
13. Click on the 'Alpha' button and Paste your digits from 8. Click on Ok when you have done this.
14. Select your geoset form the list below (where Geoset ID is written) nad press on ok.
15. Repeat the steps 11. - 14. for all your remaining visible geosets.
16. Save the model under an other name like: [name of you model]_001.mdl or whatever.
17. Convert your model back into MDX file type and you're done.
If this small tut couldn't help you, post the model here or write me an PM.
