I’ve run into this bug a few times. At some point my foliage will stop updating to the new landscape position when I sculpt the landscape. I think it may be linked to the Retopologize tool but I’m not sure.
There used to be a console command removelandscapexyoffsets that would fix the issue, but it seems to not be an option in the console anymore.
I’m fresh out of ideas, and deleting all the foliage and repainting will be a pain.
Resampling terrain size also does not work.
This was the old post that used to solve the issue for me, but doesnt anymore: