As said, when standing in a Nether portal and trying to open a chest, it stays opened, but GUI is not displayed. It is closing when opening an inventory or a chest (no matter which).
I think it is happening because you can't open any GUI while standing in a portal.

Steps to Reproduce:
1. Put a chest near the portal (no matter what type, should work on all).
2. Walk in the portal (just touch it).
3. Right click on a chest.

Tested only on 1.7.2 (I know that there is 1.11.2)