#knownfeature and maps; aka "the Disappearing Act"

[Luckmann]

So, this is starting to annoy me somewhat and I could really use some help. Using #knownfeature on anything except a starting province appears completely random. Of course, things are rarely actually random, so if someone could explain it, that'd be great.

If I use #knownfeature on my home province, it works out great. I can put anything there, be it some underwater castle magic site or a forest in a barren - I always, 100% guarenteed, get whatever I try to get.

But when I do it to a province that's going to take a couple of turns to get to, it appears completely random. SOMETIMES, the magic site is there. SOMETIMES only 2/3 of the magic sites are there. SOMETIMES there's no magic sites at all.

Is there some system to this that I'm missing? I'm trying to make a custom map with a lot of pre-placed magic sites (i.e. if the map shows a building, cave, tower or pillar there, odds are that there'll be a cave/mine, tower/pillar or other magic site there - at least that's the goal).

What gives?