Glitched billboard?

[Shadowfied]

I'm working on my custom story, and in one room I have an empty painting and I use a billboard of a picture to make it look like a painting (I'm not interested in knowing how to make a model with it instead, at least not right now) and it works perfectly but for some reason there appears a copy of that billboard in the start of the map but there's nothing there in the level editor. Even if I remove the billboard in the level editor it's still there in-game.
Here are some screenshots..

Here's what I have created with the billboard and painting, nothing wrong here:
(Click the pics for full size)


Here's the billboard that appears in the start of the map in-game:



Here's the location of the billboard which appears in the start of the map, and no billboard or anything can be seen here:




Any idea what's causing this? I've tried restarting the game multiple times, reloaded the map etc.

Thanks in advance.