[Freeswitch-users] ZRTP issue being hard to track

I make currented the production fs a few weeks ago, because i've been unable to run a zrtp call between 2 csipsimple UAs( it is an ostn setup ). Trusted mitm works, but once i enable proxy-media the UAs ignore the zrtp-hash. One of them always says 'other side doesnt seem to support zrto'. I talked on irc to steevenielson to ask him any hints and he pointed the only difference between me and ostel.me setup is the rather old version he has. Could you elaborate with me on this?