Thank you for your help, but strict exclusion is not intended to be applied here because all the non-limited users need to be able to see the unreduced data if there are no matches. Anyway I checked this setting and made a test but the problem persists.
I have delved into the problem, and it is not related to non-present values of the dimension as I thought.
Namely, there are 26 possible values that need to be restricted for the dimension, and 22 of them are properly reduced by the section access, but 4 of them are not been limited. One of the four cases is what I mentioned that the dimension value is not present in the rest of the model, but in the other three cases the value appears, so I have no idea what is really happening.
Have you ever run into the problem that your section access does not work just for some values ?
Finally the problem was related to an internal mapping that transformed the original value for the dimension, and it was not properly applied for the section access related field.
The reduction was not applied for some particular dimension values because they are not present in the data source and only appear after applying a mapping that was missing for the section access related field to limit for this dimension.
It was difficult to detect since the field shown in the document for this dimension was properly mapped.
Thank you all for your help,