I have this issue as well it seems Unreal uses very high values to store landscape coordinates. Not sure why. To solve this you can calculate your own uv’s in the material editor.
Put you landscape material node on LCCT Custom UV0.
Now in the material settings itself (click on the main material node to see them) set the “Num Customized UVs” to 1 (I have 2, but you can just set it to 1).
You will see an extra input appear called Customized UV.
Hook up the following setup:
The constant 300 value is within how many cm the texture will tile. You could make a scaler out of it to make it more accessible for artists.