Do your placed meshes have collision? In the Static Mesh editor, press the Collision button in the Toolbar and you should be able to see a collision box. If you don’t, you can create one by going into the Collision menu. You also want to make sure your mesh’s Collision settings in the Details panel are set up to block World Static.
Does your landscape happen to be steep? There are some known issues with Landscapes and Collision, and steep parts of landscapes are particularly prone to the bug. A lot of the conversation regarding landscape collision bugs can be found here:
You can export a heightmap by right-clicking it in Sculpt > Target Layers and choosing Export to File. This will save it as a .raw file which you can then reimport onto another landscape. I’m not certain this will solve your problem, but it’s certainly worth a shot. Please let us know if it does.
Okay, so I created a new landscape using the heightmap you provided, and did not encounter that log message. I spoke with one of our Landscape developers and was told that the message “Not RF_WasLoaded” refers to the fact that this component was just created, not loaded from disk, which is normal for a newly created landscape… so we’re not sure why that’s happening. Does this still occur in your level after saving and reloading?