1.  Write a concise summary that clearly states the problem. 

Villagers and Minecarts (possibly other entities) are disappearing after Logging Out.

This problem has occurred since the 1.18.10 update, has happened with both newly created (since the update) and previous to update entities.  It seems to not ALWAYS occur with all entities, but randomly villagers / minecarts will disappear.
We are playing on a Microsoft Realm, Minecraft Bedrock Edition, Survival mode, from the US and UK.
this is NOT a Duplicate of MCPE-144208, as this issue, as confirmed by [MCPE Mod] AULDRICK:
"This is the same set of symptoms as MCPE-144208, but it's not the same issue because it has a different cause." 

2 A.  Precise steps to reproduce the issue. 
EXACT/PRECISE conditions are unknown.
  2a-1.  Do not attempt to reproduce using your development environment.  X has already indicated you can not replicate in that environment
  2a-2. In a Production Environment (Mcdonalds wifi, external (non-Mojang) internet access) create (preferrabley with an XBox) a Realm for Minecraft, in Survival Mode, using any seed, or contact me for the specific Seed we use
  2a-3.  if using our seed, proceed to the village at X, Z (or nearest village if random seed).
  2a-4.  Build a library, 
     2a-4a making the interior spawn-proof for hostile mobs, 
     2a-4b ensure that Library is controlled access (double gate system, or scaffolding access only) 
  2a-5. begin to populate the library with librarians 
     2a-5a. create segmented areas with stone fencing, with 2 beds and 2 podiums per cubicle, but do this 1 librarian at a time
     2a-5b. work with each librarian (one at a time) to secure a different enchanted book at level one (put up podium, cut it down if not desired book), ensuring that Mending and Unbreaking are the first 2 books/librarians created.
     2a-5c Continue until 24 librarians are created, (can be 1 floor with 24 or 2 floors with 12 each floor as we created)
  2a-6.  Concurently, build 2 closed loop minecart systems
     2a.6a. each loop should contain a minimum of 40 rails, with at least 8 powered rails (using redstone blocks or torches) per loop
     2a.6b. each loop should have a hopper collection system as a part of it
     2a.6c. each loop should run with 1 hopper minecart
  2a-7. Save and Quit the realm upon completion, or even during the creation process if necessary (it can take some time to get the right books)
  2a-8.  Close out/power off the Xbox
  2a-9. return 8 - 12 hours later, powering on the Xbox, entering Minecraft, and joining the Realm created (again from an external internet access)
  2a-10.  Verify that all 24 Librarians are there.
     2a-10a If they are, then repeat steps 2a-6 thru 2a-9, preferably with a minimum of 1-2 hours of elapsed time between joining and leaving the realm.
     2a-10b If there are any missing, you have recreated the issue.
 
2 B.  After listing the steps, clearly state what happens, and what you believe should happen.
   2a-10a is the desired result - all librarian villagers remain every time the realm is entered.

3. Include the exact text of any messages 
    No error messages received