Blocks disappearing

Ever since updating to Minecraft 1.16.0, I have been having really strange things happening in our realm with both entities and blocks despawning. There have been other instances that I have attributed to either MCPE-21416 or griefing by a 10 year old boy, but MCPE-21416 only applies to entities that are on a chunk boundary whereas this is definitely a different glitch.

The example I am describing below is in a realm associated with my 10 year old son's account. Since he and his friends are all under age and in a private realm, they use both their real names and their gamer tags on signs in the world so I will not attach the realm backups to this issue since that would risk exposing PII. Additionally, the screenshots that I have taken have had signs with PII removed.

The problem I am describing here is a with the missing carpet and displaced cats.

Before: The two pieces of red carpet are located at (333-334, 33, 225). The cream colored cat is located at (334, 33, 225) and the black cat is located at (335, 33, 226).

After: The red carpet is missing, the black cat is missing (but no stray has replaced him in the village), and the cream cat is now sitting on a different chest in the other room.

At first, I thought maybe one of the players was griefing me (the realm is my son's but I built the village where the red carpet is missing), so I looked at all the players positions and inventory using an editing tool. (We have a "no griefing Mom" rule.) The following list is the locations of each player who was active in the realm during the timeframe for when the carpet went missing.

Player 1 -
8:30 (606, 64, 397)
9:00 (600, 65, 357)

Player 2 -
8:30 (505, 80, 315)
9:00 (598, 62, 354)

Player 3 -
8:30 (601, 57, 371)
9:00 (608, 65, 375)

Player 4 -
8:30 (615, 63, 650)
9:00 (626, 67, 647)

None of the active players is close enough to my village for those chunks to be loaded. I am the only player that is located in that chunk and I was not logged in between 8:30 and 9:00 this morning. I asked my son (who was chatting with the players via a zoom meeting) and all the active players were working on their bases this morning which matches with their locations. (I have a mapping of each player's server id to their real name.)

The red carpet was generated as a part of an igloo. The cats were tamed by me but are not name tagged. I've also had other strange things go missing and I have had some villagers and fish despawn, but after looking at the coordinates, it is possible that those entities were on a chunk borders.

This is a really frustrating issue. We've had issues in the past with players griefing and stealing which is why I now keep tabs on who's who. It is really hard to build trust when things like this happen through no fault of the players - especially since I have limited tools to inspect what's happened and address any misbehavior.

Please contact me if you would like the realm ID or copies of the backups.