Custom avatar uploader - Security Checks Failed?

Im having this weird issue where uploaded avatars appear in game as “Security Checks Failed”. Why is this, and how can I fix it?

Im working on a program that can upload avatars provided by avatar creators as a more secure way to upload private commissioned avatars to clients accounts.

I generate the vrca file via the SDK inside unity using the Build & Test button inside Unity, then uploading the resultant bundle from my appdata.

Unsure if the output file here is any different than would be generated and uploaded with the Build & Upload button, maybe its missing some critical information?

The code for the program can be found here GitHub - ArcaneBlackwood/VRChat-Avatar-Uploader
And the code responsible for uploading the avatar can be found here.

Hopefully someone out there has some idea of why this is happening! Thanks for reading :two_hearts: