When I join my realm, I expect to see my base.

But I sometimes end up in a perfect square(which I believe are possibly chunks) hole in the ground in which the  blocks which were previously there are invisible and walk-through but present. If you walk into an area where blocks previously were you would suffocate to death.

It seems to be usually about 1-3 chunks.

It usually happens in my home(spawn) or where I spawn in as I join the realm.

Relogging rarely fixes this.