Thanks for posting. I believe this is a situation that we have been troubleshooting through a regular Adtran Technical Support ticket. The notes indicate that the problems persist, regardless of if the SIP proxy feature is turned on or not in the Adtran unit.
Given how verbose the debug output and/or packet capture is likely to be with BLF and ring groups, this is likely something we should continue to troubleshoot with the Technical Support ticket. However, feel free to add any updates or questions you may have on this post. I would be glad to help out however I can.