Jakub,
I think when you say ‘agencies’ you mean Account. I think you are seeing duplicate values from your Contracts model since it is grouped by both ‘year_quarter’ and ‘account’. When you do a lookup where ‘account = A’, you have multiple rows of ‘A’ for 2018_01, 2018_02; etc.
Since the Model Lookup function only supports ‘lookup’ on a single field, try adding a Model UI field on your Contracts and SalesPlans models that concatenates the ‘key’ that you want to match and bring into your UI only model. That is, something that combines the ‘year_quarter’ and ‘account’.
Thanks,
Bill
