have the same issue, seems a bit random when it kicks in, now I unmounted the disk device (I am copying disk from old server to new one). 70% of the time the job queue seems to work and finish and let me create a new job. when it doesn't it just blocks from doing any file activity on the mounted disk. I managed to stop the array and unmount and remount and it let me start a new job.. not the most elegant way of doing it.. I haven't yet looked to find the right process and just kill that.. definitely think this needs looking at.