I was stuck today when trying to upload some textures I created in Substance Designer. No matter what, I could not successfully upload two of the three images. Each time it would result in a fail: code 400, with the one 502.
I thought it may be that the name was triggering the auto moderator, but even after name changing the upload was not possible.
Remembering that you could upload individual images to the website, I tried that instead to see if it would work there. Turns out, my file size was too large and that’s why the uploads were rejecting!
All that needs fixing is displaying more detail as to why the upload is rejecting, because it had me stumped for a little while.