Hi guys,
We just fixed a new bug in 4.7 where collision for landscape components containing XY offset data (generated by the Retopologize tool) was broken. The fix will be in 4.7.3 which should be out next week. If you’re using source code you can apply the fix directly before then if you’d like:
https://github.com/EpicGames/UnrealEngine/commit/cbaaca1e870bce1aae32ba5d0c7dcd48c7b6aea2
Cheers