I had a similar issue with this too. Heres some background (Granted you are windows and we were on AIX)..
On 8.4.0.3, we ran ARSMAINT on our two object servers every friday night. After we went to 8.5.0.6, the ARSMAINT would run via our scheduling tool (Autosys) and give a return code 0, we would see the hits in the system log for ARSMAINT running. Our first fix after working with IBM for a while was to run the ARSMAINt command on our Library server compared to our OBJECT server. This worked fine in the lower tiers but once we tried rolling it out into production, we saw the same issue that you had.
We logged on to our OnDemand servers via SSH/putty, and the process account that we used was the same one that ran the arsloaders and other pieces.
I believe the fix (And I apologize, I am NOT familiar with how security like this works in windows) was to give SUDO access to whatever account is running ARSSOCKD, to "Run as the instance owner.."
I hope this make sense, if not let me know and I will try to clarify a bit more.
Thanks
Jeff