There is an out of the box O365 video portal which you can use instead of using normal document library or Assets library.
You can even manage the user channels:
I was able to reproduce this issue and was able to fix it as below:
You needn't specify LinkTitle name, its not needed.
In schema.xml, I changed the ContentTypeRef to ContentType and added the fields
Modify the content type tag in elements.xml as below:
yes, the culprit here is "alternate access mappings" in the central administration. make sure the AAM mappings for the web application/site collection is having correct url pointed in the correct zone with proper bindings.
if there is any problem with the AAM settings, then site collections behave in a very odd way especially for editing.