I have been noticing this ever since 1.18 and frankly was hallucinating because they are rare and random, but this is happening on a multiplayer game (playing local with my wife) and it already happened enough times for us to conclude it is a bug.

Areas (totally random and not necessarily cubes, seems more like spherical) are missing from time to time, they seem to be between 2 and 8 blocks in radius at totally random spots. I initially thought that maybe it was an exploded creeper but it happens always in areas I built and are well lit, not to mention, nobody had creepers in there. The latest one (screenshot below) is FLOATING and cannot have happened to a creeper explosion.

The first happened in a wall, a spherical area including a village wall, house and all of the contents inside this sphere were missing including a named fox.

The second was in the top of a tower, the whole top of the tower was no longer there, except for a floating copper rod.

But this one made it quite obvious something is wrong. The whole roof of an observatory tower is gone, also with the tip still there (screenshot). Notice it doesn't even look a spherical void, more like random.

We always notice this after a reload. 

I cannot replicate it on purpose since I already mentioned they are random in place and time.