Digium B410P, beronet 2S0 misdn RELEASING CHANNEL

Many times per day while speaking the line is dropped and “RELEASING CHANNEL” message is written in misdn.log.
I’ve checked all cables, interference problems, isdn lines and tuning but I managed nothing.
The problem seems to be chan_Misdn

MISDN HANGUP PROBLEMS ! Wed Jul 25 10:06:53 2007: P[ 1] * RELEASING CHANNEL pid:31 ctx:macro-MyO dad:s oad:2109635723 state: CONNECTED ... INSTALLED VERSION MISDN Misdn General-Config: -> Version: chan_misdn-0.3.1-rc34 -> misdn_init: /etc/misdn-init.conf -> debug: 3 -> tracefile: /var/log/asterisk/misdn.log -> bridging: yes -> stop_tone_after_first_digit: yes -> append_digits2exten: yes -> dynamic_crypt: no -> crypt_prefix: ** -> crypt_keys: test,muh -> ntdebugflags: 0 -> ntdebugfile: /var/log/misdn-nt.log