The nether portal at my base does the same thing. When I step into the portal, the animation doesn't appear. I had to travel a great distance in the overworld to finally be able to travel to the nether. I appeared out of the same portal as the one I use with my base (although the one in the overworld was VERY far away). Now Im stuck in the nether. I tried to build another portal and break the original but still not working.