Cold River map disconnect

There is an area in Cold River map where, if you put a portal down, will result in disconnect every time you try to get back in the map.



Putting portal down in this area before engaging the boss will result in aforementioned behavior.
This is likely due to the fact that, before engaging the boss, this area can be freely traversed, however, after the boss fight starts and until it ends, it can't be entered - you have to click the door travel point which takes you straight to the circular arena.