I had and just avoid same problem
- click “./Packages/com.vrchat.base/Editor/VRCSDK/Dependencies/VRChat/API/VRCTools.cs:101” on error message to open VisuakStudioEditor.
- insert " return; " statement at 1st line of “internal static async Task IncreaseSendBuffer()” function ( at next line of “{” , before “var servicePointScheduler = …” )
- save file, then Unity will run auto-rebuild of SDK script by detecting file change.
- you should be able to upoad avatars
This function is explained as “expanding send buffer to speed-up”, and cause error. So we should have no problem to skip this function’s process, just slow-down.