Encountered a problem, my linked_portal_door's don't want to partner up, keep getting this error:

prop_portal_linked_door 'portal_1' failed to link to partner named: 'portal_2'

The thing is, the linked_portal_door's are in an instances and that may or may not be the issue. As I already had done this in one of the instances (2 instances, both have linked_portal_door and are connected) and it had no problem, but for some reason this happens to few linked_portal_door's. Ofcoure if I put the linked_portal_door out of the instances, it works.

So where is the problem here? Why some linked_portal_door's work while others don't? Should I re-create the instances?

The problem is definitely in the instance part of it. Change the fixup name on both of the instances, and set that as the name instead. So, say if you fixup-name the instance "instance_1", then your portal can be referred to as "instance_1-portal_1"without issues.

Alternatively you could rename the 2 portals to have @ in front of their name so name fixup is not done at all. Go into the instances and rename the portals to @portal_1 and @portal_2 then reference those as the names instead.

I would imagine that this is because of the prefixes. I would either rename the portal doors to include an '@' before the name, or set the instance to not have a prefix. That's assuming you don't want multiple instances of this instance in the same level. If you do, then I would add a parameter to the name, so you can specify each as a different one.

Just looked it up, linked_portal_door's inside the instances which were working had a fixup name, the ones that didn't work - didn't had one.

Great, thanks for the help.