Does anyone have any more information on this problem?
We're still trying to find the root cause.
I've ran a strace on the process:
Process 166598 attached - interrupt to quit
10:13:26.697084 select(5, [4], NULL, NULL, {0, 415000}) = 0 (Timeout) <0.419247>
10:13:27.116602 getppid()...