Parked Calls dropping

Have a strange situation where a call comes in and is answered no problem. Call is then Blind Transferred to parking lot 70 (default) and the call appears to be successfully parked, the caller can hear on hold music etc. and the BLF shows a call parked. The new recipient then dials 71 to pick up the call and it appears to be bridged in the CDR reports but neither side can hear audio then the call ends. We are on version 13.0.120.

Have pulled the logs but I cant determine what may be causing the drops.