Rideable Animales Disappearing from the Overworld

I been having this issue since the new update, my donkey has been disappearing after being 15 seconds in the overworld.

this might be affecting the donkey being too long in the nether so when i return to the nether the donkey was there, i put him back in the overworld and then 20 seconds later he disappeared and he reappeared back at the nether.