Great question! No, I usually don't have a problem loading a smaller map when not using a mod.Just out of curiosity:
You mention that every time you start a new map it fails to download said map, for all 8k maps.
Does that mean you only ever generated 8k maps, or have there been - apart from once - other maps that failed or did not fail to download ( Navezgane, PREGEN0X, 4k, 6k, whatever)?
Not trying to derail, so here is the mandatory disclaimer: and, of course, logs!