I’m not really familiar with this specific CSV importer, but it seems like you are trying to make changes to a customer for each line. However, you are importing 11 lines whereas only 1 customer object is available. You could try passing on a list of customers for which you want to make changes.
Alternatively you could try to have the import action return a list of non persistent objects (one for each line), without any input parameters. When you have these objects you can just use whatever data is in there to retrieve the user from your database and make your changes accordingly.
Hope this helps!
Thank you for your answer. I followed your proposal using a workaround – I skipped the parameter and committed the objects within the sub microflow.
To me, it seems to be an issue related to the specific CSV importer (or my personal configuration). In the app I want to read line items per customer and the relation Customer – Detail is 1-*. Once I add the parameter (even before executing the sub microflow), I get the exception.