A single piece of code has been identified at the root of this, which was uploaded earlier today. This has been removed/fixed and the problem should not surface again.
Apologies for any inconvenience this may have caused. If you need a race re-run please request it in the race re-run thread.
UPDATE 2: It seems that we did in fact resolve the issue before 20:00 GMT, however, the delays at 20:00 GMT had a totally different cause, related to maintenance work on the issue overlapping with the races for that hour, which set in to motion a similar series of events to 19:00 GMT. The issue has not repeated at 21:00 GMT which confirms that the fixes applied at 20:00 GMT have worked.