Tired of the Penumbra "Reserved Files" issues❓
Me too! and Unfortunately, the Pythia Body Mod has this issue as well

Since no official fix exists yet and it seems the mod hasn't been updated in a while, I created a fix for myself and wanted to share it with you.
I don’t want to cause any trouble, especially regarding copyright.
If you are a user who has no clue about file replacement, you can reach me out on Discord (lunneafriendship) and ask for
the repaired Modpack from Pythia (only the .pmp file). However I will not upload the complete repaired Pythia 3 Modpack in this thread.
Instead, you will get a repaired Penumbra meta.json file (which you can always find in your Penumbra Mod folder after installing a mod) and a files/common/35/pythia_skin_mask.tex/ file. Both files are required to fix the Pythia 3 Penumbra "Reserved Files" issue. The rest of the Pythia 3 files work without any problems.
If the mod Author
Scherana [The Moon] 3D updates her Pythia 3 and fixes this issue in the future, I will remove this mod fix.
How to patch Pythia 3?:
1. Go to your Penumbra Mod folder.
2. Search for "[Dark & Moon] - Pythia 3.0 (A Bibo Compat Multi Size Gen3 Body)" or "[HS] [Dark & Moon] - Pythia 3.0 (A Bibo Compat Multi Size Gen3 Body)".
3. Open this folder. You will see a files folder and a meta.json file (TexTools/HS users will find a third file there).
4. Open my packed fix file (manual patch for pythia by Lunnea.rar).
5. Extract the "files" folder and the "meta.json" file from the archive directly into your Pythia 3 Penumbra installation folder. Confirm and overwrite the existing files.
6. Reload your mods in Penumbra or restart the Game.
The error should be gone now❗
Please note that this fix is only for Pythia 3. If you have redirection errors with other modpacks, this will not help you.
Please note: Every reinstallation or new installation of the mod Pythia 3 will overwrite and remove this fix, so you will have to apply it again.