Dropdown filtered by a list

hello everyone, I recently had a problem which I largely imagine was solved by the forum post: Constraint: list-to-list

but now I’m in a new problem. Basically my goal is to filter a dropdown according to the filters I put in a multidropdown.

For this I created a “thing” called “disease”, within this “disease” I created a list of “symptoms”.

after creating some diseases with several symptoms I would like to create two dropdowns, one of which has all the possible symptoms that I defined and the other dropdown should show all the diseases that refer to the symptoms I chose in the first dropdown.

I used the form presented in the post, and I managed to filter the search, but my problem is that when I choose the saved symptoms, my disease dropdown doesn’t return anything in any case:

and the output with the selected symptoms:

can anyone help me?

Thank you!