Dataset does not refresh when EM1 is assigned to workspace

Client has EM1 sku with PBI embedded.
Client is using Vena connector.

Almost 12M rows worth of data. 

Now, Power BI dataset takes 30-40 minutes to refresh when it's a regular workspace. 

Power BI dataset fails with EM1 is assigned to the workspace. 

Error: 
Data source error: 

DataSource.Error: <pii>Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.</pii>. ;Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.. The exception was raised by the IDataReader interface. Please review the error message and provider documentation for further information and corrective action. Table: values.