I don't remember it being dodgy as such, and have been up and down it many times without concern. It doesn't quite reach the bottom of the shaft though as I remember, which can be a bit of a pain for short-legged people. I guess the only certain solution would be to remove it completely and either replace it with a new one or install anchors to make it suitable for SRT or electron ladder, but that may be controversial, as the fixed ladder does make it more accessible to the less athletic who may benefit from the visit, writing from personal experience.
There are some fixed ladders around on pitches that would be far more serious than this if an accident occurred, as it is in a fairly narrow shaft. Egnaro Aven for example - that's about a 20m unprotected drop into empty space if you screw up, but I've never seen anyone lifelined up or down that.