Just to give a little help, I am showing the result of a single texture LTA_wall02.tpc in the game. Hard to know now how many other textures could be affected, but I know for a fact that there are at least two more in the LTA_wallxx.tpc series of textures.
Normal camera:
First person view camera:
UPDATE: I converted the texture LTA_wall02.tpc into .TGA and checkid it out with GIMP. There is no problem with the Alpha channel. So when I tested it again in TGA format, the issue was gone! This reinforces my dislike for .TPC textures. In the past, I have had bad experiences with them and gave up on the idea of converting the massive amount of HD textures I have in TGA format into TPC just because of that.