I was going to bring these up in my thread about joining a motorway, however just found this.
I was approaching junction 25 (southbound M1) yesterday, and I knew it would be busy because there are so many roadworks on at the moment.
My plan was to go past it and come off at 24a to avoid the traffic. As I was getting closer, none of the overhead gantry signs were showing warnings (such as "queue on slip road") as they usually do. I thought this was a bit odd. At the 1 mile marker, there were still no warnings of traffic so I prepared to come off at 25. I couldn't see ahead due to the bend, but still maintained a speed of about 55 mph at a good distance from a HGV.
As I got around the bend in the motorway (about 1/2 mile from the junction), I saw the slip road up ahead completely full of traffic with vehicles queuing on the hard shoulder. There were also five vehicles sat completely stationary in the live lane 1 sat indicating waiting for a gap! For me that presented the huge risk of a potentially fatal accident. The fact that there were no warnings at all on the approach to this junction baffles me...
Unsure if this was due to the failure of a system as mentioned above, but it was alarming.