Unexpected error: Evaluation was canceled

I am facing the same issue now. I found one of possible reasons at Microsoft TechNet (https://social.technet.microsoft.com/Forums/en-US/f55b83a9-a966-46a4-80fc-2cca08fa3a12/unexpected-error-evaluation-was-canceled?forum=powerquery) 

The answer says: "

Do you have background analysis disabled? If so, these errors can happen but should be purely cosmetic. The reason they happen is that the editor side pane depends on analysis results. If you mouse over one, this starts an on-demand analysis evaluation. If you then mouse over another one, the previously started on-demand evaluation will be canceled and show the error triangle.

Let me know if the errors interfere with the loading of your data to the workbook or data model. That would be a bug." 

However, I am not sure what backgroud analysis means. I did uncheck the "Allow data preview to download in the background." I am wondering if this could be a reason why this error keeps happening? 

I unchecked this to speed up the refreshing speed, since I am importing lots of CRM data from the datawarehouse. It would be painful if this is the root cause...