A few strange issues to report, all semi-related:

• Pioneers stacked with another unit sometimes consume the wrong unit (peasants and great bears so far) when I tell them to build on a resource out of my influence.
• If I don't leave a unit on a resource, the building simply vanishes.  Doesn't seem to matter if I wait around for it to finish building or what, it just vanishes the turn after there isn't a unit directly on the resource.
• However, after loading a game when I did leave a unit on a resource, the building still vanished.
• That said, things still get weirder - while trying to reclaim the resource multiple times, I eventually gave up... but noticed I was getting a ton of guilders per turn.  My gold mines seemed to exist in memory even though they didn't exist on the game map.
• I'm pretty sure the same thing happened with the +5 tech research building, because for a while I was getting really fast research after I'd lost the building on that resource.  But when I reloaded, research went back to normal.