How to enable SOA serial increases for API changes

[buzanits]

As I understood, the setting:

pdnsutil set-meta example.org SOA-EDIT-API INCREASE

Should increase the serial after every change to the domain example.org via API. I use lego which is a letsencrypt client that sets TXT records in pdns for DNS challenges. I can see the new TXT record in the pnds mysql database. But the serial is not increased. Which prevents the secondary DNS to not sync the new record. What am I doing wrong?

[Habbie]

That should work. Can you show your zone (please do not change anything in the output) before and after the API call please?