configManager.serviceSystem returns null from time to time

Hi,

i have a workflow which restarts the sfcbd-watchdog if there is a problem.From time to time i get null on reading configManager.serviceSystem. The system is alive and with powercli this is working (get-vmhost <hostname> | get-vmhostservice | ? {($_.Key -eq "sfcbd-watchdog")} | restart-vmhostservice). We are using vCO 5.1

Any ideas ?

TIA

     Thomas