I tried to edit the Shivgoroth Form's transformation into a new custom tile, but it didn't quite work out as I was expecting...

I mean, I added a new .png file to the npc image folder and edited the talent timed effect to show the new tile, but it just made my character invisible. I did double check if the file name or file size were wrong btw.
Then, I returned everything back to the original state and decided to purely edit the Shivgoroth's image file itself... by just pasting the new sprite over it...

The new one fits the 64x128 size, has a similar shape as the original one and I haven't touched the file name or file size or the skill algorithm. Yet, my character goes into Elemental of Stealth mode again.
So... What's the deal?
Happy Christmas btw