I can't say for sure what's happening, but I do see an irregularity in your setup:
Some blending happens with, I think, a distribution shader, while that hasn't had any compute terrain/normal happening before it.
That output is being used somewhere else below in the screenshot and perhaps also further downstream out of view?
I'm wondering if the whole thing is being calculated correctly.
So if it turns out to be working correctly and as expected by you, then my next guess would be to either use the last shader which goes into the planet as the "sit on" shader or place a compute terrain with small enough patch size at the very end before your planet and only use that for your populations (and not into the planet node).
I run into these cases very rarely, but if I do then I have never been able to solve them, strangely enough.
