Object reference not set to an instance of an object

I had a similar issue with my data model where everything was working fine in Power Query, but upon "Apply changes" I received the error. I started to disable the load for all tables and left only my main fact table. The error message changed and showed an error with a data type mapping. Apparently something in the DB backend had changed and the data type could no longer be correctly applied. In the end it would help if Power BI Desktop could provide better error handling on this.