Linked filters not working and strange behaviour on multiple joins with the same table

Hello, I'm trying to apply linked filters on columns N1 -> N2 to filter by multiple levels of a hierarchy in my data, which looks like this:

All the columns in this image are rows in a custom fields table identified; if you're familiar with WordPress, imagine the table user and usermeta. So in the source database, those fields look like:
id | userid | fieldid | data
1 1 10 Manager
2 1 11 Operations Department
3 2 10 Seller
4 2 11 Sales Department

Given the shape of the data, I use subqueries to retrieve each one of these fields alongside the user's data. Since it's easier to do so with pure SQL, I created first an SQL query and based on that saved result I created a Question with GUI builder.

I was following the tutorial from the docs on linked filters and saw it used a dropdown filter with the option From connected fields to retrieve the values, however it is empty for me:

Even with From connected fields being empty, the dropdown filter for N1 still shows the values and filters the table correctly.

However, the linked filter feature is not working as N2 filter still shows all the values when the table is already filtered by N1:

I thought maybe it doesn't work with Questions, so I tried to convert it into a Model, but the situation is the same.

Then I tried the example from the docs, with the Sample database and State and City fields and it worked perfectly. So I thought, maybe it doesn't work if my Question or Model is based on a previous SQL query, hence I tried building my query entirely with the GUI builder as so:
(Had to remove image due to limit of 5 reached, but it consists of a main user table joined 9 times with user_info_data table)
I said earlier that in my original SQL query I used multiple subqueries from the same table to get the custom fields (N1, N2, company, position, station, and some others). In total I join the user table with user_info_data 9 times to get all the requiered custom fields and it produces the desired table.

Now when I tried setting the filters on this new Question I created, it becomes complicated to select the fields I want (N1, N2), but I know they are the last 2 so no biggies (I tried changing the name of the columns but it doesn't show up like that in this part, only the default table and column name, if theres another way to rename it please do tell):

After I map the filters to the columns N1 and N2, I went to check the From connected fields in the dropdown for N1 to see if it showed data like in the docs. To my surprise, it appears to be pulling the data from the first join to user_info_data which retrieves users's IDs (I covered the values as they're personal info) and not the values corresponding to N1:

The field from user_info_data which holds the value is data

My guess is that since all these values have the same column name and come from the same table, perhaps internally when matching to the filter they are treated the same dispite the appended suffix like _2_2_2_2_2 to the table name.

Sorry for the long post, but I wanted to share all my unsuccesful attempts at linking filters for N1 and N2.

Is there anything I'm missing to have data show up in From connected fields to succesfully link the filters like in the docs? Thanks a lot for your time :v::cat:

are those fields from the same table? is that a SQL or a GUI question? which dw are you using?

Hi, the columns on the filters come from joins to the users table (which is the main table here).

I first tried a SQL query to perform the joins to get the columns to filter by, and the based on that SQL query I created a GUI question and then a Model. On this GUI question and Model the linked filters didn't work properly. Then I tried generating the same query via the GUI only with many joins from the same table. Here I got the problem with values from the wrong column showing up on the dropdown.

I'm running the queries on a MySQL db from a Moodle instance. That's why I'm performing a lot of joins to retrieve the data as it's normalized in a relational fashion.