Suddenly falling through LandscapeStremingProxys


I’ve been working on an island for awhile and have never seen this bug.
I also cannot find answers online.
I was working on an update for my island and all of the sudden (I didn’t change the landscapes settings) I fall through certain LandscapeStreamingProxys for no reason. I’ve tried clicking “Build Landscape” but that doesn’t fix it. This happened about a month ago and actually deleting the landscape and rebuilding it was my only fix, which was a huge waste of time, but the problem keeps re-appearing and I don’t know how to resolve it.
Someone please help!
Thanks.