Had a computer attached to QCN but set no new tasks. Suddenly I find a QCN task running. This computer doesn't have a sensor so there is no reason to run a task, but sometimes I use it to check stats. In any case I aborted the task and hit update to report the abort. Event log says, not requesting tasks. Switch to the task log and there is a QCN task running! How did it get there? Went a bit more and suspended QCN and toggled the NNT setting off and back on, just in case. Aborted the task and hit update. A QCN task in the task list, suspended at least, and again the log file says not requesting task nor is there any mention of a task download.

As the computer has no sensor, I detached which fixes the issue for me, but leaves some strange bug in BOINC that allows tasks to appear and run but not be logged as to how they got there!

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Depending on which BOINC version you run versions 7.1.18 and 7.4.8 had fixes for the NCI NNT problem. I'd say, check you have all Activity 'based on preferences'.

It would perhaps also be a thing to see a scheduler contact in work, so add <sched_ops_debug> and I don't know, do NCI tasks get sent through HTTP contacts? If so a bit of <http_xfer_debug> would probably be nice as well.
Oh, and BOINC version.

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