I came upon a very odd issue which I wanted to share in case it happens to anyone else.
I was trying to import a valid oData feed from a SharePoint list (validated OData Validator) and tableau was telling me it was an invalid oData feed.
Well I had no other way to figure out if the feed was invalid other than attempts to import to Tableau, given this was a 1900 item list, I started using orderby and top to find out where the bad apple was in the list. After a lot of searching, I found an item which had a  in the text field.
is the representation for a vertical tab. Apparently, although it validates as a valid odata feed, Tableau does NOT like
After removing the instances of  the feed worked fine.
Hopefully this might help anyone who has a random 'invalid odata feed' with a SharePoint list and they don't know where it is coming from.