Take a look at this: http://blog.nyphonejacks.com/2013/04/network-clean-up-overhead-paging-and.html

A nice example of what we often find. Mind you I’ve seen a lot worse. Not only is this installation difficult to trace out but it’s prone to damage. A little known fact is that so many network problems can be traced to dodgy patch leads. Patch leads that only make an intermittent connection, those with the retaining tags missing (a favourite one that..) and patch leads that simply do not work. Some leads, for no apparent reason, just die from old age. The motto? When in doubt, chuck ’em out.