I don't know how to find output logs, but not being able to drop friends +/only worlds is annoying. I would select a portal from my favorites, change instance to friends or friends+, place the portal, then the "portal" will show up then disappear within a few seconds.

On a side note, I remember dropping a "broken portal" would force the main menu to shift right making it unusable when the beta first dropped. I don't know if you already fixed the menu issue or if the bug is rare (since some friends and I had the issue when the beta dropped) but recreating the portal bug didn't break my menu when creating this report.