Error using Sharepoint Migration tool

[Vgoss]

So I am using the Sharepoint migration tool to move us from sharepoint 2010 to sharepoint 365. However each time I run it, I get the following Error: 

Invalid site URL 'https://portal.gwisr.org' (ErrorCode: 0x0201000F) OriginalMessage: Server Issue when doing SP Query Entity (External Content Type) cannot be found with Namespace = 'https://portal.gwisr.org', Name = 'Recon Account Numbers'.

Any help on this would be great.

Thanks in advanced

[#2]

@Vgoss  I've had this issue with a corrupted Site Column and followed this blog to resolve the problem. The migration tool wasn't able to read the one of the Site Columns

https://jshidell.wordpress.com/2012/06/07/removing-a-corrupted-site-column-in-sharepoint-2010/

I am not 100% sure if you can migrate External Content Types. 

The error code indicates it's a site access issue but in my case it was just one item in the site it couldn't access.