The converted book file can't be corrupted while being uploaded, because it was never uploaded. It is the identical book that is being delivered to the ultimate customer. If it looks good, it is good.
You can of course upload a Kindle Preview or Kindle Gen -built mobi to the KDP, let it mill about, and download the converted book to check on Kindle Previewer. But that seems rather duplicative to me. You are doing the preview twice.