With traditional British relay-based signalling there is a risk that a wrong side track circuit failure (showing clear when occupied) can cause a train to disappear from the system, allowing signals to clear behind it, points to change ahead of it and even other trains to be given conflicting routes. Solid state interlockings generally got more protection, especially if used under Automatic Route Setting, and the ARS* itself monitored the occupation of track and on detecting an anomaly would raise an alarm and stop attempting to set routes in the vicinity.
*This is based on the original British Rail IECC when I was involved with it up to the early 90s, but I assume later systems and those from other suppliers were similar.
