Tash Scheduler / Job Queue NAV2018

I would like to get some insights on the complete story:

Until NAV2017, it seemd that I could control, which user runs which automatic jobs.

In NAV2018, it seems that the all users run all jobs, regardless if they have the permissions required or not.
I have errors in the log where a "Job Queue Entry" was processed by a random user 30 times within one minute (and always fails, obviously).

Target is:

I have two jobs to be scheduled:

* Adjust Cost job (running nightly)
* Communicate with external service to pull documents from a web service (every 10 minutes).

These jobs require certain permissions.
Therefore I scheduled the jobs with a certain user ID. Nevertheless, the job is picked up by a random user and processed in a background session.
Is that a bug or is the job queue useless for this type of automatic jobs?