I had an occurrence where I was not able to enter  the portal from the south side. 

The portal was  surrounded by three walls on the west, north and east sides.

So I blew up the wall on the left side of the portal and was able to enter the portal from the west side.

Yeah, I have seen that bug before but it's super hard to replicate and I'm not sure what causes it. Definitely one I'd like to fix for sure!