Unfortunately, I’ve the same problem with UE 5.3 as well, on below instance:
I tried to create a new landscape with reduced resolution (232x232 to 113x113) and so, the number of components reduced from 1084 to 64. I had to do that to reduce the draw calls, as the original landscape is heavy for mobile platforms.
WIth new landscape, I tried to reuse the heightmap & layers from the original landscape (by export / import). All went smooth, I could see my original landscape’s cliff / terrain on the new landscape - all ok, except the player collision. It still remembers the original landscape collision and player walks on the air this time 
Build all / landscape, etc… didn’t help.
I’m yet to try rebuild the project from scratch, will update.
Thanks,
Rush At Games / Roxroria (available on Steam)