Comment 12 for bug 536149

This is for bzr5904:
I upgraded an imperial iironore mine to a deep ironore mine.
There was a masterminer working in the oremine before I started the upgrade.
The economy did not have any spare masterminers, nor any spare miners,
but it did have 4 spare pickaxes at the warehouses.
I did not upgrade any other mines while this was going on, to avoid any confusion.
When the deep iron ore mine was built, my masterminer entered there and took
the lower slot, and I got the "worker missing" message.
The empty slot was marked as "vacant" not "coming""
I then built a coalmine, occupied by a newly created miner.
I destroyed this mine, but the miner did not move into my deep iron ore mine with
the vacant slot.
Only when I created a new masterminer at another mine and destroyed it,
the deep ironore mine was satisfied.
\widelands\tribes\empire\deep_oremine\conf has:

[working positions]
master-miner=1
miner=1

but it seems that for some reason a deep mine expects 2 masterminers.