Quote: "I've experienced a bug I've never seen/heard before. All my entities from the first 2 levels have vanished. Only doorways and rooms are standing."
In fact it's a rather common disaster. It happens when for any reason the contents of the "files" folder are re-arranged. It doesn't matter for a built game of course but any maps (=.fpm) are affected, since they load all media from the path they got it originally.
I am talking of experience. After having downloaded tons of free media from the forums and the major free fps websites, at one point I decided to neatly restructure everything. I did put creatures, entities, vehicles, etc. in seperate folders and renamed segment folders accoriding to the content inside. As a result all of my maps suddenly where missing some (or most) of the media.
I guess most of us did that mistake in one or the other way at the start.
In case you find my grammar and spelling weird ---> native German speaker ^^