Well known trick to reset work to 100%: somehow get out
_all_ lazy civs (convert, shoot, move, load, ...).
Then repopulate with industrious civs. This is okay,
except for the load/unload trick, which allows you to
repopulate with the very same civs, miraculously made
industrious by the ship.
Same problem for loyalty.
Same problem for land units. The stock game's land units can't carry civilians, though.
Root cause: unlike sectors, ships and land units don't track civilian loyalty and work percentage.
Related bug#3539284.
They also forget when flown in. Related bug#3539285.
Unload includes scrap.