How do I make Darth Nihilus become transparent and gradually fade away as he disintegrates in the game?

[Erdan5]

Hello.  So a while back, I made a post called "Dumb question, but what graphics are required for a smooth dissaperance in a cutscene?".  The post basically was about the way Darth Nihilus fades away as he dissolves into a red "cloud" of dark side energy.  Back then, I didn't have the game yet, and now I do.  

There are some playtrhough videos on YouTube of KOTOR II, both TSLRCM and TSL vanilla, that have Darth Nihilus fade away gradually and become transparent before completely vanishing in the red cloud. The way he vanishes into the scarlet red dark side "smoke" looks super clean and transitions nicely, his model fades and becomes more transparent as he fades away in the cloud.  However, there are other playthroughs of the game, both vanilla and TSLRCM, in which he doesn't vanish the same way as others.  Instead, he just glitches out of existence after the dark side energies combust out of him without fading gradually and becoming more transparent.  His model just stays the same before he just pops out of existence in the cloud.

I really like the effect where his model becomes transparent and fades away in the cloud, as it looks more realistic and looks like a visually stunning effect, but in my own personal playthrough of the game, my fear was true.  He just glitches out of existence, the one where he doesn't become transparent.  I made a video of what I want the death of Nihilus to look like vs what I have in my actual game.

I want to make him become transparent and fade out gradually, but I don't know if it is graphic or resolution issues or a script thing.  To give you more context, here is what I have on my game.

I have the GOG version of the game, (Good Old Games), specifically the GOG Galaxy version of the game. I am running this on a Nimo Gaming laptop.  I had installed TSLRCM to my computer, then I installed the Unofficial TSLRCM Tweak Pack, specifically the tweak that removes the Visas Marr and Mandalore conversation on the Ravager and makes the cutscenes run like in the vanilla game.  The footage you see is from my game with those mods installed.  I then began to wonder if this was a product of the Tweak Pack and/or TSLRCM, so I uninstalled those mods and played the save game of that level vanilla, but same result, (to be fair though, I was playing from the same save after I uninstalled the mods, so I dunno). 

This is all REALLY weird because I myself am making a mod where I use the sithritual001 effect on Darth Sion in the final battle level with him on Malachor V, and he has the transparent gradual fadeout but somehow Nihilus doesn't.  You can see a snippet of my "earlier revision" of the Darth Sion mod here, where he is seen fading out and becoming transparent. 

I want to find the root of this problem, mind if anyone helps me please? Help would be greatly appreciated.