Linked_Portal_door Render Glitch
I have a linked portal door connecting two hallways, to make a paradox type thing were you end up in a room that is looking down from where you were before you walked through the hallway. Anyway, there are some observation rooms in the second room that when looked through the linked portal door the frames are not rendered, but when you tilt your screen so you are looking at the obs. rooms and the linked door, then they are rendered in the linked door. Basically my question is, how can I make the observation room frames stay rendered even when I'm not looking at them directly? btw they are func_dynamics
Generally looking through linked portals are going to be a major problem, especially with visibility of props and other objects. Multiple views through the same world portal can also create some major issues. The main reason why objects disappear and appear depending on where you look is because of of visleafs.
Now you could fiddle around with func_visclusters in order to determine where and what is visible, but I guarantee this will produce other visibility and performance issues.
Your best bet is to change your puzzle and get rid of the world portals. They are buggy and usually confusing for the player.
Thanks ChickenMobile the func_visclusters did the trick! Also I know linked portals shouldn't be used in puzzles I was just making a little fun coop map to do with friends just to make their brains hurt. 
I know the issue has been resolved. I just had to add a comment on what ChickenMobile said.
First, when you fire a portal, that is technically a world portal with a texture over it. The blue (or orange) swirling ...thing... you see around the opening is merely an animated texture that Valve overlayed on the World Portal.
Second, LINKED world portals are not the issue. The issue is the game engine. Yes, a linked_portal_door renders things oddly. However, a regular world portal does the same thing.
Valve never tested the visual stability of the world portals because they were not planning to use them in the final game. They failed to think about the fact that portals fired from the portal gun have the same problems since they are essentially the same thing. So using world portals will remain problematic until Valve gets off their collective butts and fixes the game engine.
As to being confusing to the player, speak for yourself ChickenMobile. Not everyone is going to be confused by the shift in spacial orientation. After all, some of the puzzles in the retail game RELY on this effect. I, for one, do not have a problem with reorienting myself in space like this.
Actually, there's a rather large difference in the code between how normal portals and world portals are rendered. Since a lot of code is shared I would consider them both portals, but use the word "world portal" to refer exclusively to a linked_portal_door entity, and "normal portal" for a prop_portal.
What I don't get it that I'm 99.9 % certain that I have used linked portal doors in the past and I could see the props through the portal even if I wasn't looking DIRECTLY at them, but through the portal. I've seen other maps do this to and I highly doubt they used func_viscluster's for everything, so do I have another problem, or have world portals always worked this way and I just haven't noticed yet?
EDIT: Also the func_viscluster's have stopped working and I have no idea what I did. Could someone explain to me the "proper" way of using them so that I can keep a prop rendered even if I don't look at it so I can see it through the world portals?
Try making a visclusters with two brushes, one filling the room on one side of the linked portal door, and the other filling the room on the other side. Tie these to the same entity so that you will always guarantee one room will be rendered while you are in the other. Hopefully this should help without impacting the performance too too much.
Portal 1: Portal Pro, Resurrection, Dyad, Rexaura
Portal 2: [Coop] Electrophobia, [PTI] EotM Collection, [SP] Aperture Halloween
I've tried everything but for some reason the visclusters just stopped working. The only thing I've done before it stopped working was add a coop start and finish room. Do you know what could be causing this problem?
EDIT: I have removed the coop rooms so it is just like it was when it was working but the visclusters still won't work no matter how I put them. Could there be some sort of setting preventing it from working?
your graphics settings will change how many portals are rendered through, but you just have to accept that maybe you will have this problem =
I actually wonder why they had to "improve" the graphics options screen and remove ability to tweak amount of rendered portals and stuff like that.
The HL2 kind of options menu would have been better for low-end machines as you wouldn't have to keep shader level on minimum because of overused reflections, bloom and swaying vegetation.
I apologize for off-topic.