I tried to bring over my videos from my dolphin site using the dolphin to UNA migration tool. It has been spinning for 3 days and nothing is migrated. The videos are mostly youtube embeds - could that be the reason?
Then explain the spinning for three days. If the site is mostly YouTube embeds it shouldn't be spinning for three days. I am helping someone migrate Dolphin to UNA; against my advice, and yes, the migration is horrible. After a day of trying to migrate profiles with about 1/4 migrated, today the profiles are gone. I contacted the owner to see if he removed the profiles and no. My guess it must have been the migration script.
This usually happens when connection between servers times out or is broken while transferring. May not be your case... but look into transfer speed and timeout settings. When we do assisted migration most if The issues are related to data transfer between hosts.
I saw many different servers with different servers' settings and script may work on them all. It can not be run by themselves and to delete the profiles. If so, then there is something horrible with server and server's settings.
You need to check bug report emails and server's logs, may be Dolphin script from which you trying to transfer info has some modifications and there are some errors.
If you can not migrate, provide me please with access info I will check.