"For example, the door across from the Transporter Room in season 3 (also previously mentioned upthread) changed colour and a few episodes later in LTBYLB was actually shown to be a working Turbolift! It also changed colour later that season back to the regular blue. Much better IMO, it's a weird place for a turbolift stop!"
While the door color changed to red after "Elaan of Troyius" the scene you are describing from "LTBYLB" appears to take place on main deck 3 (across the studio set
of the transporter room). The corridor end has this strange angled-in wall (they used earlier in this episode for the hangar deck) they put there some time during Season Two or Three.
The movement of Lokai and Bele throughout the ship (monitored and commented by Spock on the bridge) suggests that the turbo lift is inoperative below deck 3. It could appear that the transporter room is on deck 5. Which - again - might indicate that's where we have sickbay. I feel that medical wards and transporter rooms should be on the same deck so you don't need to worry about moving those stretchers and get injured landing party personnel to an "astro-medicine ward" ASAP.