I guess this answers the firaxis programmer's comment about whether to take this out!
Thanks jdog, that was quick! I'm glad it wasn't something I did, because I was wracking my brain trying to work out how my change could cause the observed behaviour.
EDIT
A question for LunarMongoose.
Could you perhaps let me know how you fixed it? As I said before, for me this was tinkering in unfamiliar territory so I have no idea how frequently the function is called and so whether I need to try and cut down on (possibly?) expensive functions and repeated calculations.
Besides, your fix might be more elegant and i wouldn't have to have it commented so weirdly as a fix by me for PIG Mod but from mongoosesdk.
By the way, I also don't like how I reassigned iMinAreaSize but I wondered whether it was necessary to create a new variable or not? (or whether I should)