Hi @RodrigoDiaz and welcome to the Quick Sight community!
Since you’re already filtering down the months, what happens if you remove ‘Month’ and ‘Year’ from your calculated field..would that resolve the error from showing up while still providing the correct information?
If this does not work, it may be more helpful to assist further if you’re able to upload a copy of your analysis (with anonymized data) to the Quick Sight Arena view since I don’t have a sample dataset that’s similar to run tests on. Here’s some additional information on how to set that up: