Teragon v0.50.11.0 is released. The main change is that it will generate a checksum file that will prevent the game from using half_splat images of terrain, causing roads to look bad or disappear altogether.
So what are half_splat images? They are new in 1.0 and I don't know exactly why they were added, but they are a processed image that take your road and water maps and shrink them to 50% the original size. So an 8k map becomes 4k. This doesn't change the map size in the game, but it does cause a loss of detail, especially for roads. Many thin gravel roads can partially or fully disappear on your map, and if you're making your main roads be less than 100% road so that they look slightly overgrown with grass and dirt, this can make those roads look extremely patchy. There may be a good reason for them using half_splat images, but they cause a lot of problems. Even on my RWG map I started with in 1.0, my gravel side roads were often missing. I could see where they were on the map, but there wasn't any gravel where the road should be. In the forest, I could see where they *should* be because the grass decorations and stuff weren't on them, but that was the only indication where the path was as it was just the grass terrain without gravel.
Here is an example of what half_splats can do to roads. And in this one, they didn't entirely disappear, but they still look really bad. And even if you think this looks okay in the snow (snow covering the roads), it looks really out of place in the other biomes.
The update for Teragon should prevent the half_splat problem from happening. If you still have problems, let us know. You'll still run into this kind of problem with RWG, though. Hopefully TFP will either remove halt_splats or find a way to not have this issue.
Note that although this does also impact rivers, rivers are usually wide enough that you won't notice. If you had a river that was very narrow, you would probably see a patchy river as well.