Summary: I recently built a Iron Farm its in two different chunks in my Minecraft World it was previously broken after I found the reason why it wasn't working it would mean that every time I (The Host) leave the world the villagers have a chance to unlink from their workstations and lose their job but relink to their or a random workstation as you join back into the world which breaks the iron farm because with this multiple villagers can switch workstations when they are supposed to be linked to a workstation in their pod in the iron farm causing the player to have to destroy all their workstations and relink every villager until they are linked to the right workstation every time the Host leaves the world.

Steps to Reproduce:
Step 1: Build a Iron Farm or Villager Trading Hall in two different chunks or even a Villager Breeder with the required amount of Villagers.
Step 2: Link all the Villagers to Beds.
Step 3: Link all the Villagers to Workstations.
Step 4: Afk for 10-15min.
Step 5: Rejoin the World.

Observed Result: Villagers can Unlink from their workstation when the Host leaves the world this bug relates to many other villager related bugs including villagers de-spawning with workstations and villagers randomly de-spawning. If you understand villager mechanics then you understand that villagers are unable to de-spawn if they are linked to a workstation. Though as soon as they lose their job or they are unlinked from that workstation they have the ability to de-spawn or change to another workstation and breaks any villager related farms that involve workstations such as the iron farm I built below because the villagers swapped workstations.

Expected Results: Villagers shouldn't be able to unlink from a workstation if the Host of the world leaves the game as a result of this bug it causes many other villager bugs to occur such as villagers having the ability to randomly de-spawn or villagers de-spawning with workstations which is this bug report MCPE-21416. Furthermore if the player were to build a iron farm with a lot villagers they shouldn't be able to forget they are linked to that workstation or have the ability to randomly switch their workstation for another one.

Related Bugs:
MCPE-21416
Iron Farm Tutorial:
https://www.youtube.com/watch?v=ZOxzJpBK_BA