DataMart refresh fails when try to add another (SharePoint) source to existing data mart.

I have created 2 DataMarts with ODBC(Redshift) data using a common gateway, I was able to refresh both successfully. But, when I attempt to add another data source (SharePoint) to one of the data marts, it started showing error and refresh fails. (Note: I have not fully connected to the SharePoint and imported any data, I have just clicked on 'Get Data' option, choose 'SharePoint folder' data source, entered the SharePoint URL. Click on next, it showed me the list of tables, I just stopped at this step and cancelled the process).

Now my data mart has become useless since it is not getting refreshed and/or there is nor provision to delete the tagged data source.

The other DataMart connected with ODBC(Redshift) which is using the same gateway is refreshing successfully.

I have another data mart with only SharePoint data which is working fine too. This issue is occurring when I try to combine 2 different data sources in a single DataMart. 
Can somebody help me to fix this, Please let me know if you need any other details, Thanks in advance.