Many mobs disappearing (even name-tagged villagers)

We are seeing a large number of mobs disappear in a long standing world on the PS4.

We have a 2nd village and none of our 7 villagers were there.  All were tagged and used for a gold and XP farm.  All were secure behind iron doors, no chance of lightning as we have rods and no evidence they turned in to Witches.  No items, and no way in to their trading hut.

We then travelled to our main village and ALL the sheep, ALL the fish in the aquarium and most of the 30 or so villagers also had disappeared. Some of the Pandas had also disappeared but not all.

We take backups and can see in a previous copy that it didn't happen all at once as we have 2 villagers still in existence in the small village and the rest are missing. So this must be gradual.

Game size is 366MB (too big?).  It appears to have happened after spending quite some time in the nether gathering Netherite in 2 player split screen mode. 

We also noticed 2 trident killer farms lost their tridents but believe this bug may have been rectified ❓ , however this mob bug is ongoing as we see some mobs missing on the 18th October backup and more missing on the 19th October backup.

We still have the copies if needed and can provide photos etc. I also have access to Realms if copied needed.