Bind9 keeps crashing when forwarding is enabled

I have a debian small server setup with bind9 and dnscrypt both on the same machine. Bind9 runs on port 53, dnscrypt on 5000. The regular bind9 server performs some checks then forward the requests to the dnscrypt one. It worked fine until now however since some days it can't boot, and crash with the follow lines showing in journalctl -xe Mar 19 16:00:46 myhost named: ../../../lib/dns/name.c:2487: REQUIRE((((dest) != ((void *)0)) && (((const isc__magi Mar 19 16:00:46 myhost named: #0 0x559ba65cbd80 in ?? Mar 19 16:00:46 myhost named: #1 0x7f0525f9e9aa in ?? Mar 19 16:00:46 myhost named: #2 0x7f0527688f36 in ?? Mar 19 16:00:46 myhost named: #3 0x7f05277069ba in ?? Mar 19 16:00:46 myhost named: #4 0x7f052770828e in ?? Mar 19 16:00:46 myhost named: #5 0x7f05277085e1 in ?? Mar 19 16:00:46 myhost named: #6 0x7f0527764bf5 in ?? Mar 19 16:00:46 myhost named: #7 0x7f0527774591 in ?? Mar 19 16:00:46 myhost named: #8 0x7f0525fc2a23 in ?? Mar 19 16:00:46 myhost named: #9 0x7f05259694a4 in ?? Mar 19 16:00:46 myhost named: #10 0x7f0524dbad0f in ?? Mar 19 16:00:46 myhost named: exiting (due to assertion failure) If I disable the forwarding option inside **/etc/bind/named.conf.options** it works back again, once I enable the forwarding it crashes. forward only; forwarders { 127.0.0.1 port 5000; }; What it could be? I tried to understand better if is something cache related, if I could clean the installation and get back to the working status but nothing... No matter if i try to forward the requests to another server like 208.67.222.222 OpenDNS server, it crashes the same. :(