At first should be useful to post your message at firstname.lastname@example.org group. By the other way let me advice, to make an explained detail of your problem as;
Asterisk version Openr2 version Configurations files Dialplan dahdi pattern detail Detail of the call process (inbound or outbound call failed?)
In case of outbound call failed extension dial wait time of the call process (waiting for ringback tone, busy, reorder, silence etc)
call trace log (for better collect information, you could move or delete old data log on /var/log asterisk/…..)
In case of inbound call failed, it could be possible with call log and monitoring bit CAS signalling
Based on your explanation and information could let you know the possible reason of the weird issue.
By the other way, let me explain when dahdi restart, it make hardware reset, therefore will stop card control software and restart again, these will cause lost frame connection between you box and PSTN, and call process, etc. When dahdi restart again it recover frame between both side and set CAS control channel according to dahdi parameters setting on system.conf These is for preventing to let to PSTN start call handler process during asterisk starting process or stop. Another point it seems on your log information a call have been answered, so it seems is working.
PD: 0x00 it doesn’t mean idle state (it mean force release)
Mc GRATH Ricardo E-Mail email@example.com