There are two things which might have occurred regarding the boom barrier. The wiring is tied to the wiring of the interlocking system. So they may have swapped cables (yes, often the cables are just incorrectly /confusingly labelled and it's very easy for someone to inadvertently swap them), resulting in the interlocking system thinking that the point is set of main line when in reality it is set for the loop. But there's another thing which would have happened. When the boom barrier work is going on, trains would get a red signal, which is the failsafe system. Now it could be that the work was going on late and so someone decided to override the system to show a green light for the oncoming train. But forgot to change the points to the main line from loop.