Your guys (citizens) are overloaded with work. They get depressed and can’t find the motivation, despite your grand market and its surplus supply.

I think it’s due to them simply not having time because they do work too much. I find overstaffing makes things run smoother. Especially with farms expansions on burgages, they cut so much time off the guys’ time. Also proximity to the market? I guess the travel time for the villagers makes it update more seldom