Issue with bringing wolves into the Nether

I attempted to bring a wolf with me into the Nether. My Nether portal is in a tight area, so I had to push the wolf into the portal. When I did so, the wolf disappeared as I expected. When I entered the Nether, the wolf was there as well, sitting inside the portal. However, about 1 second after I entered the Nether, the wolf warped back to the Overworld. However, the wolf did not warp back to the Nether in a similar fashion. It remained in the Overworld. I had to lead it away from the portal and then back to the portal in order for it to go back to the Nether. Every time I have tried to bring a wolf with me to the Nether this has happened.

What I expected to happen:
I expected the wolf to remain in the Nether with me.

What actually happened:
The wolf went back to the Overworld

Steps to Reproduce:
1. Push a wolf into a Nether Portal, letting it disappear
2. Enter the Nether through the same portal
3. Wolf is seen sitting for a moment, then disappears
4. Return to Overworld through same portal, wolf is there sitting.

Additional Details:
I don't know if this is relevant, but I am using the texture pack vonDoomCraft version beta 2.7. I patched the JAR file with mcpatcher-2.4.2_03.