Hello,
we have our own PVP server and we discovered bug about nether portals.
If somebody go through portal, which leads to protected area (ex. faction area or residence) and portal is active, but there are solid blocks around it so nobody can move from the portal, people will get struck forever. Only some admin´s teleport can save them. The problem is, that if the player is inside nether portal, he cannot open chat, escape to menu and so on. Only thing, which works, is movement. But in cases of "buried" portal they will be struck forever. The portal canot transmit people back, unless they step from it and back to it.

The bug can also be that people won´t be thrown back even they didn´t moved from and into portal again. Or that game won´t allow people open chat or even ESC.