I've been trying to fix this for a while, but as far as I can tell from my time spent hunting for solutions in forums, there isn't one at present.

Basically, when I have a clothing mesh object that has a transparent texture and a NiAlphaProperty when opened in nifskope an equip it in-game, it renders alright. If you have a second clothing item that is positioned over the first when equipped in-game and has transparent textures/a nialphaproperty, you can see the original transparent item through the second equipped transparent item, but it now disappears at certain camera angles when you move the camera around the player in vanity mode.

Does anyone have any suggestions on this? Cheers.

I don't know anything about this, but I'd be tempted to combine the two items into one clothing item.

Already tried that previously. Even if the items are in the same mesh .nif file, they still don't co-operate with each other's transparency if they are separate objects within the .nif file, and they need to be kept separate as they use different UV maps and textures from one another.