FWIW, Factorio has a 255 tile limit. If you run over it mod tiles are just never created. The most common combo to cause problems is Alien Biomes + Asphalt Roads, but it can happen with any combo that generates too many tiles. That could certainly be the problem here. Alien Biomes is usually involved because it has, like, 196 tiles or something. So there goes most of the space. :)
Personally, I'd add a check on load that your tiles exist, and pop up a warning that too many tiles were defined so your mod won't work, if they don't exist. Easier than trying to guesswork it every time. YMMV.
