Este era um bug conhecido no software 10.2.4 BIG-IP que estávamos rodando.
Do suporte da F5:
...you hit a known issue tracked internally as: bug ID539130 "bigd can deadlock while processing SIGCHLD causing bigd heartbeat failure and SIGABRT" -=Condition=- External monitors that run for a long time and are killed by the next iteration of the monitor, may cause bigd to crash and core, this causes a temporary lapse in health monitoring.
A correção foi atualizar o software com Hotfix-BIGIP-10.2.4-HF12-866.11-ENG
.