DNSCrypt not resolving some domains

Hello,

after successfully setting up DNSCrypt on my pi-hole as decribed in github wiki: DNSCrypt · pi-hole/pi-hole Wiki · GitHub
I found some domain names unresolvable, e.g.:
reply www.bountysource.com is NXDOMAIN
using resolver cs-de.
This domain resolves using resolver d0wn-de-ns1 but d0wn-de-ns1 dows not resolve e.g. www.postbank.de.

Is it a common issue that DNSCrypt resolvers do not resolve every domain?
Can I tell dnsmasq or pi-hole to forward to a different resolver on NXDOMAIN responses?

All in all, the pi-hole works well with DNScrypt - except for some domains as mentioned above.

Kind regards

Don't know whether it's related, but check out this post, regarding DNSSEC (if you are also running this)
my log says:
Jan 30 14:50:54 dnsmasq[620]: query[A] www.postbank.de from 192.168.2.125
Jan 30 14:50:54 dnsmasq[620]: forwarded www.postbank.de to 127.10.10.1
Jan 30 14:50:55 dnsmasq[620]: query[A] www.postbank.de from 192.168.2.125
Jan 30 14:50:55 dnsmasq[620]: forwarded www.postbank.de to 127.10.10.2
Jan 30 14:50:55 dnsmasq[620]: forwarded www.postbank.de to 127.10.10.1
Jan 30 14:50:56 dnsmasq[620]: query[A] www.postbank.de from 192.168.2.125
Jan 30 14:50:56 dnsmasq[620]: forwarded www.postbank.de to 127.10.10.2
Jan 30 14:50:56 dnsmasq[620]: forwarded www.postbank.de to 127.10.10.1
Jan 30 14:50:58 dnsmasq[620]: query[A] www.postbank.de from 192.168.2.125
Jan 30 14:50:58 dnsmasq[620]: forwarded www.postbank.de to 127.10.10.2
Jan 30 14:50:58 dnsmasq[620]: forwarded www.postbank.de to 127.10.10.1
Jan 30 14:51:02 dnsmasq[620]: query[A] www.postbank.de from 192.168.2.125
Jan 30 14:51:02 dnsmasq[620]: forwarded www.postbank.de to 127.10.10.2
Jan 30 14:51:02 dnsmasq[620]: forwarded www.postbank.de to 127.10.10.1
Jan 30 14:51:02 dnsmasq[620]: validation www.postbank.dE is BOGUS
Jan 30 14:51:02 dnsmasq[620]: query[A] www.postbank.de from 192.168.2.125
Jan 30 14:51:02 dnsmasq[620]: forwarded www.postbank.de to 127.10.10.2
Jan 30 14:51:02 dnsmasq[620]: validation www.postbank.dE is BOGUS
Jan 30 14:51:08 dnsmasq[620]: query[A] www.postbank.de from 192.168.2.125
Jan 30 14:51:08 dnsmasq[620]: forwarded www.postbank.de to 127.10.10.2
Jan 30 14:51:08 dnsmasq[620]: validation www.postbank.dE is BOGUS
Jan 30 14:51:08 dnsmasq[620]: query[A] www.postbank.de from 192.168.2.125
Jan 30 14:51:08 dnsmasq[620]: forwarded www.postbank.de to 127.10.10.2
Jan 30 14:51:08 dnsmasq[620]: validation www.postbank.dE is BOGUS

I'm already running the correct dnsmasq version, so there appears to be something wrong with this domain.