No, there are definitely (at least) three positions; I am convinced now with the Savage Curtain shot (thanks, Mytran!). GSchnitzer, please review the first and third images in my previous post, taking note of how the "gooseneck wall" and adjoining doorway wall meet at the floor
; this should eliminate any camera-angle confusion. (If the angle in the Bele-transporting shot were truly 90 degrees with camera distortion, we would expect to see the other 90-degree angles in that shot similarly distorted, but they all look fine.)
Also, in the Lincoln image, the wall that supports Spock's science console cannot be parallel to the door; otherwise we would see that wall. The science console itself is angled toward the transport console, and somewhat away from the door (note that you can easily see the back of the top edge of the console, and the back of Spock's viewer).
It seems clear that the yellow-striped apex of the kiosk must be acute (in all the shots I've seen); I suspect that the two walls of the kiosk are fixed together, but the whole "prismic" thing was rotated relative to the transporter room walls on either side in whatever way was convenient each episode.