Signallers are refusing to go along with unsafe blockades.
Time was that trackside gangs could talk directly with the signal box and organise the protection they need. But these days, unless there is a failure, they have to go through the planners. So if the planners get it wrong, there is a problem - and unfortunately, they do get it wrong: putting the blockade limits in the wrong places, for example, or even on the wrong road. Of course, cuts in staffing levels don't help!
As this happens more and more frequently, signallers are no longer prepared to play ball. Mistakes in the blockade planning? No blockade!
That should concentrate their minds. Meanwhile, RMT is banging on their door to get this sorted.