I glanced at the walkmesh IG yesterday after getting the house number and can confirm this is nothing specific to an area but a problem with the tile, which is unaffected by overrides. I've not yet had a chance to look at the model, though I'm aware of the tile number in question. My assumption is that when the decor was ripped from the Bioware tiles to create the blank areas, the walkmeshes were not edited to match. The second issue - what I assume is the remains of a shop counter - wasn't visible by color, so that one will be needed as well...
The tiles in question are tin01_m03_03 and tin01_m04_03. (Incidentally, this has also been cause to notice an error with that tile group preventing that room from being used in new areas...)