I've started the eighth mission (the one where you have several barbarian tribes to the north, west, and northwest, whom you have to supposedly convert, I just haven't gotten that far into the level...) several times and each time I am unable to build the coin minter. I can lay the foundation of the building and a Builder will level it out, but my Serfs never bring resources to it to actually allow building. Has anyone else come across this?

Edit to add - I've seen the other building problem post. That hasn't helped me.

Even better - On my Nth try on this level, all of a sudden my Swine Farms stopped producing Swine. Full wheat on all of them, but also full Skins. Does having a full Skin level prevent them from producing more Swine? My population started to die off despite having less than 100 Serfs, 10 Wheat Farms, 5 Swine Farms, 2 Butchers, 1 Wheat Mill, 1 Baker, 1 Tanner....

Could be a number of things. Without seeing your setup, some things I would check...

1 - Road to the doorway. - This can sometime be confusing where the doorway is. Just lay road across the entire front to test.
2 - Road completed to the storehouse - If there are missing links in the pavement from the storage facility your diggers will clear the area but peasants will not deliver stone and wood.
3 - Adequate supplies - Make sure you have stone and wood...
4 - Worker Shortage - Could simply be to many jobs for your peasants and its a long wait.

My personal guess would be number two based on what you described.

On your second issue... No, you still should have produced a carcass for your butcher. Any production building that is full on what it produces will stop production for that item only. So your swine farms will stop making skins if you have no other building using them, a full storehouse, or a closed storehouse.

Separate issue... Your pop was dying as 100 serfs is way too many for 2 butchers and 1 baker. By at least 50 or so I would say, depending on your army size.

The above poster is not correct. Swine farm always produces skin and carcass together. So if a swine farm is maxed on skins it will stop using corn and will stop production. So you want to make sure your serfs take the skins from the swine farm and deliver them either to a tanner or store them in a storehouse.