I’ve had similar problems populating a map from a datasource call (google sheets). What I found is that the data source blocks return the coordinates as STRINGs and adds quotation marks, even though the data is stored as a number. If the addMarker block is pass a values of “123” instead of 123, it will produce errors similar to your image. My solution is to convert the data source return values to numbers by adding zero.
See if that helps
