Actually it will give you that error even with 1 tag.
I did a post and video about it. https://steemit.com/dtube/@phoneinf/dtube-is-having-big-upload-problems-error-while-submitting-to-the-blockchain
Sometimes it just stops to load the next step as well. This one is stuck and been for hours.
This is happening both in Google Chrome and Firefox browser.
it is really strange and annoying, but my error was fixed by only using 1 tag "dtube"
Nice to hear you got that working. Worked eventually for me on PC. Seems to be very random. When it works and when it doesn't. I suspect it's because the growth Steemit has seen the last couple of weeks in new users!
yours is not all lower case if you notice from the screenshot