Leashed, tamed and named mobs despawning.

The ‘semi-tamed’ foxes that I have kept despawning so I named them and put them on leashes that are tied to fence posts. However, when I wake up in the morning and check on them, they are all gone! They shouldn’t despawn if they are under just one of these conditions, let alone all three. They could not have been released by another player as they are well hidden and, anyway there was only one other person in my world and they didn’t leave my sight. They couldn’t have died either as I was not presented with a death message.

I am aware that Minecraft Bedrock on the Nintendo Switch is prone to strange occurrences (e.g. the whole world turning purple, every tool becoming an enchanted arrow, entire chunks being in eternal night or simply not existing, disobedient bees, lag, random crashes, lag, fearful zombies, lag, odd teleportation etc.) so maybe my original foxes are out there somewhere...

Also, they did not have much space to move in, which I have heard makes a difference.