Halted production and then unable to staff

I halted production at Blacksmith. Cannot recall if I removed the staff, but I do not think I did. Later I un-paused - but now there are no staff and I am unable to add staff. I tried restart, no luck there, and p5 did not correct.

Do you have enough labourers spare to fill the slots?

absolutely… it just ignores when I hit the plus icon to try to add staff back in

Did you set a limit on any production of items? If so then that will stop production and they won’t go back to work until the minimum limit is exceeded.

I very likely had production ratios in place, but no storage limits. (the blacksmith items are all 0 to infinity)… I did set a storage limit on tallow early on in the game)
The ratio definitions seems to have gone away - but local storage(in the building) are showing last-produced items (swords and axes) and raw materials (coal and iron bar)
What is happening when I click on the + in the occupancy pane(to add a worker)… one of the slots turns from Slot Disabled to Unfilled (rather than filling in a worker).
I also noticed that the building has a pause symbol versus production halted symbol on it.

I had a thing last night where the Arborist refused to keep a 2nd worker for more than a few seconds. Repetitively clicked the worker in, and kept denying them.
It was late, so I just saved and decided to check the next day after turning everything off, and it worked fine.