Reason: you used the salt number the same value as Dungeons Crawls mod
While you can reduce this by setting the separation to another number it still generates frequently in the same location

maybe another salt value could help

dungeons.json
dldungeons.json

I didn't realize that -- I never looked at the salt for Dungeon Crawl. It was the maker of Dungeon Crawl who help figure out how to plug them into the new structure system. I guess he used the one for his own mod, and I didn't realize or think to change it when I re-implemented the dungeon features.

Versions before for 1.12.2 and earlier used this to find dungeon locations:

		mrand = new Random(world.getSeed() + world.provider.getDimension()
				+ (2027 * (long)(chunkX / factor)) 
				+ (1987 * (long)(chunkZ / factor)));

2027 * 1987 = 4027649

So I'll try using 4027649 and see how that works.

There, done -- that should do it.