I was doing a few laps of the Barbarian Outpost Adv. Agility course and ran into the glitch outlined here (Player clips into room below crossbow and gets stuck until logout).
I didn’t log out to attempt to fix this and instead teleported back to the Outpost using the Runescape Gold Games Necklace and found myself on the roof one square away from the location the teleport should have taken me to.
It turns out I wasn’t on the roof but actually just walking around on the ‘floor’ level above the ground. I was still restricted by obstacles like trees and walls on the lower level as normal, but couldn’t interact with any objects (including doors) and NPC*.
I then teleported in Lunar Isle and then Al Kharid, both times finding that I was still floating above the ground unable to do anything other than run around.
I logged out which seemed to fix the issue, then teleported back to Barbarian Outpost only to find the same thing happening again.
Logging out or into the lobby and back fixes it, but it’s slightly annoying (and kinda fun)