Reverse DNS lookup issue in parsedmarc

Haven't used this tool for a while but I love it! 

Got it up and running again and noticed an issue with the reverse DNS lookup.
I was spooked when seeing a bulk of our mails originating from outside our tenant's data zone but when crosschecking it turns out to be false.
In this case it is exclusively IPv6 source IPs that are not looked up correctly.

Anyone having a similar problem?