phpIPAM + PowerDNS: Invalid response from server: 422 Unprocessable Entity (500) adding VNET subnet

I'm trying to create a 172.16.0.0/16 subnet from the 172.16.0.0/12 address space. I have created in phpIPAM the 16 zones, 16.172.in-addr.arpa. through 31.172.in-addr.arpa already.

But when I'm trying to create the subnet in Proxmox, it reurns:

create sdn subnet object failed: can't read zone 16-31.172.in-addr.arpa.: Invalid response from server: 404 Not Found (500)

Although I'm using only the 16.172.in-addr.arpa zone. So I tried to create a zone named 16-31.172.in-addr.arpa...

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