Automation: One of the intentions was to give each NPC a "toolbox", adding and removing tools as necessary. And dumbbell wasn't part of any tooolbox
so it was removed at nights. Fixed in code and coming in 0.30.
Ideally the automation would only take care of items declared as job tools and ignore any other item.
Else it create problems, mainly for example you can't have any optional job tools (non mandatory items but increasing performance if present, I had the problem with the binocular for my slaves hunter).
I'll have the same problem if I want to add an optional whip to the mistress job, increasing submission of slaves.
It would also solve the problem of the dumbbell which would be ignored, because declaring it as a job tool even if it is not is an error and will conduct later to dumb code the more the game advance.