[Freeswitch-users] Freeswitch stops handling register requests

Hello, We faced today the following situation: Freeswitch suddenly stopped to respond to answer to REGISTER requests. At the same time it created more and more channels. A lot of them „hung" in status „RINGING“, after some time all calls were rejected with 503 Maximum Calls In Progress. After a restart, everything went back to normal I cannot find any WARNING or ERRROR/CRIT messages in the log. Also there is nothing special in the syslog at the time the issue appeared. We are using freeswitch 1.6.17 on debian jessie installed from debian packages. Calls are handled via esl / mod_event socket. Is there any known issue with this version? Is there anything else I can check? Thanks and Regards Markus