Andoid-App does only IPv4 no IPv6

Hi, I'm based in Melbourne Australia, and we have been using the NextDNS services for a while now and am wondering if the Andoid-app might have a bug.

with the NextDNS Android App ON, I get strangely IPv4 only responses DOH: https://nextdns.io/diag/fb7eda60-dd57-11eb-9677-d1ec2c70d7b0

With the Android App OFF, my router resolves NextDNS and, I get IPv4 and IPv6 responses DOT: 
https://nextdns.io/diag/4f707510-dd59-11eb-9677-d1ec2c70d7b0

Not sure how to finetune, any help?