M6 Southbound J17 Overhead Speed Sign

[Taozzz]

The overhead gantry speed signs (the one with 4x individual screens) on M6 southbound between J17 and Sandbach service seem to be showing NSL all day, even when there wasn't any reduced speed limit up stream. Does anyone know why?

I just got startled by it yesterday, thinking if there's the NSL here, did I miss the reduced speed limit earlier? But then looking around at the rush hour (5pm) traffic around me, they can't all have missed it as we've been travelling down together like packed sardines since Manchester, and I don't remember anyone suddenly slowed down as they would after seeing a lowered speed limit.

[Glenn63]

Because they’re all useless and don’t work properly. Often still showing changes to limits, lane closures hours/days after the incident.
Few weeks ago one was saying ‘caution queue 40mph’ for days even at night when almost no traffic about.
M6 south where toll and M6 come back together it’s 5 lanes, signs above where;
40-X-right arrow-50-left arrow.
What are people supposed to in that situation it’s ridiculous.

[Taozzz]

With this one, Traffic England's website has a 'traffic report' page that shows what's currently on the gantries in real time, and this particular one has been showing NSL all morning just like yesterday when I went past.
https://www.trafficengland.com/traffic-report