Data refresh keeps forgetting credentials - OData

The refresh fails with this error: Processing errorThe credentials provided for the OData source are invalid. When I go to Schedule Refresh - I see errors with some credentials. Then I enter them one-by-one when there are no errors, but when I again open some source that I've just entered valid credentials for (Basic authentication) - it shows "Anonymous" as if it has forgotten what I've just entered... Sometimes, when trying a lot - I do succeed, but rarely. It looks like a bug, but I doesn't allow me to go Production and all the Power BI project is a NO GO :( Please help Thanks, Michael