addOneTimeTask weird behaviour


We are having trouble with scheduling a task in our IS through the WmPublic/pub.scheduler:addOneTimeTask service.

We are able to add the task and we can see it listed on the IS page, but when the startime/startdate is reached it displays an error:

[ISS.0026.9201] Unknown service: Siebel8PerfTests:execSPT

If we add the the task manually through the IS page it does not display any error, so it seems to be an issue with the addOneTimeTask service…
The service does exist and is located at the correct path provided.

Note: Updates installed
Updates IS_7-1-1_Audit_Fix1

I would appreciate an insight into the what the problem might be. Let me know also if you need more information to understand the problem…