Why does landscape distort when saving in 4.19?

First of all, the landscape was once fine. Then I noticed a slope became ragged, somehow.

When I save the landscape, it pops up, creating slopes above its collision, causing pawns to sink into the landscape, and in some cases, disappear into it. If I touch any part of the landscape with a single click of (for example) the Smooth tool, it goes right back into shape. When I save it, at the very end of the save, it pops the landscape back up, into the previously bad, incorrect state. This also causes curved peaks to become jagged, and the ragged effect on the above-mentioned slope, which was created using the Ramp tool.

I see others had this problem in earlier versions, but the suggested LOD changes only make it blocky and worse. I also noticed it was marked as a bug, but that thread ends without resolution.

What is going on and how do I stop it from happening again? A huge time-waster that makes it hard to work with UE4.

I’m going to answer this in case someone else has this problem. There was a box brush area below the landscape that was about 2X larger than it should have been, extending beyond the mesh it was intended to be under, placing it in close proximity with the landscape at one end. When I shortened the dimensions of the mesh to fit, the landscape quit misbehaving, and I haven’t seen it err since.

This may not happen in 4.20, but it sure messed up in 4.19.