I tried to bring my cats through a portal and afterwards every time i enter the portal i got disconnected

I was going through nether in my friend's realm and made a portal in nether to explore the over world and i found some animals on the other side .. i decided to bring some back through the portal i have prior described. i used a lead to get some cats in (parrots were fine) and they went through but when i tried getting into the portal to get into nether it disconnected me from the server every single time so i can't go back now.