I think it is almost inevitable. I have posted to other sites myself but I always thank the original poster both on the original site and on the new site, except where I download from usenet and it gets difficult there to fit a thanks in between a lot of spam sometimes. It annoys me when people pretend they did all the hard work when they are just using other people's stuff

I've experienced for years that either the upload succeeds (if it is a relatively small video file) and then some sort of error meesage or if it is a bigger file taking very long to upload it times out with another failure message. Sorry, don't remember the wordings of the failure messages, don't do that often  >:D