I encountered the same issue again, this time inside a Trial Chamber.
The missing terrain did not reappear when I approached it, and a large part of the surrounding terrain became invisible.
My previous report, MCPE-241987, was marked as a duplicate of this issue.
I have attached a video and screenshot showing the problem.
The same issue also occurs inside a Trial Chamber. In this case, the missing terrain did not reappear even when I approached it.
Seed: 3098906679398689017