Random Point Failure with platform changes ( or reversal movements / wrong line where a route permits it ) Random Thunderbird Duties using you Stock to help train (DMU'S ) - With Dynamic timetable changes to new expected times and announcements on train ( big ask I guess ) Diversion due to blocked line where the train turns back and become a Northbound/Southbound services Blocked Level Crossing Line Checks ( suspect trespass ) Congestion of backed up trains due to early delayed services Emergency Passenger Cord Pulled Flooding / Subsidence ( rivera line ideal ) Guard being able to make Additional announcement ( could mean extra point of for delays , or problems etc )
At least two of those (blocked level crossing and line checks) can be implied to be a reason for a signal delay.
