Hey Julius
I think the problem is because of the way you are storing you meta values.
For example in ACF you have the field chili
and in there you have the choices which look like:
Senza risposta : Senza risposta
1-5 kg : 1-5 kg
6-10 kg : 6-10 kg
11-20 kg : 11-20 kg
Più di 20 kg : Più di 20 kg
On the left side is the internal value stored in the database, and on the right is the label that is shown in the admin.
I think the spaces on the left side are causing an issue.
Could you do a test with another new custom field (just for testing purposes) which has no spaced on the left side, or alternative modify the above to:
Senzarisposta : Senza risposta
1-5kg : 1-5 kg
6-10kg : 6-10 kg
11-20kg : 11-20 kg
Piùdi20 kg : Più di 20 kg
And then update some posts with the new field values…
Does that make sense?
Thanks