ERROR: Accept Socket error with OD4.5

crusader

Salutations,
we've had to hurriedly roll back from OpenDeploy 5.5 --> OD 4.5 on our target server (which we had to swap). When we do a command line deploy from our TeamSite server to here, the files go through (and we see that in the log files on both sides) but then it writes endlessly "ERROR: Accept Socket error" in the target log file, until it runs out of space. Have tried various included decreasing the verbosity, redirecting etc, but still have this problem. My understanding is that OD 4.5 is now no longer supported, so I was wondering if anyone out there can dig deep to remember this error.
Many thanks
C