I was experiencing a UGC validation error seen below earlier while uploading shoes, however, there was no visible attributes in any of the descendants of the layered clothing shoe that I was then uploading.
I then ran a print for the attributes of the handle in question using the command line, which returned this:
Upon closing the Bundle Auto-Setup window, then reimporting, my shoe layered clothing was able to pass UGC Validation. There was a hidden attribute created by having the window open that prevented me from passing UGC validation.