I have had the same issue. I normally refresh and start from scratch if it hasn't uploaded in ten minutes. In regards to the thumbnail, I use their take a snap function and it behaves smoother on the upload. Steemit has had a lot of denial of service attacks recently as has Dtube so some days it has to be left. As it's early days these issues are being sorted out so hopefully it's not a permanent thing. It is rather time consuming but certainly worth the effort to post your videos. On other notes, I don't know if you caught @dollarvigilante recent interview with D Larimer on EOS but you may want to give it a gander. It's a great crypto summary and extremely informative. :)