coastal hamlets spawn both on ice(both perma and some of the ones that end up being water 20-35% of the time) and in the void.(along the edges of the map)

Many thanks, I'll look into it

I'm found bug with coastal hamlets spawning on ice.
Seems to be Frozen Sea belongs to the group -42 = land locations.
So I fixed the event code by just adding line -terrain 346
Now it looks like this:

squareevent
+terrain -17
+terrain -42
+terrain -105
-terrain 346 #must be NOT a Frozen Sea
+player 28
+varlesser 18 280
+minturnnbr 30
+seasonleft 3
+season 1
+chance 1
+squareowner 24
-armyowner -3
newunits -3 "1d6*Levy"
makestationary
alterterrain 78
endevent

Well done, I haven't touched this in quite a while now. This might help a lot of people that feel this exact pain point as well.

I've encapsulated your change along with some extra checks to re-introduce some mechanics