Close to you is loaded landscape, past that line would be unloaded landscape, they are out of sync.
I don’t know if landscape has its own HLOD thing going on seperate to build HLODs, I did assume so because landscapes always seen on a map with no HLODs built
I wonder if build HLODs does anything to it
Maybe related to your landscape collision issues ???
If you find each landscape tiles UASSET file & copy them somewhere else with file explorer…
Would deleting the landscape tiles and pasting the copied UASSET files back into the outliner, force it to rebuild something ???
Thats a big job though, I accidently deleted a landscape tile once and had to go back to a previous version, find the UASSET, save it somewhere, restore latest snapshot and then pasted it in.
Not so bad with 1 tile, but a 8x8 grid of tiles is 64 files to find.
A simpler thing to try could be to delete the landscape tiles then use undo to bring them back, I just tried it on a landscape tile and it does calculate something when you undo the deletion.
Only try if your confident with windows file explorer and have a snapshot to fall back on if it goes funny.