In excess of 40% of decisions by ATOS, the medical assessment company, are being overturned at appeal.
So it seems likely this is being repeated across the country. And there's certainly no shortage of individual stories in the papers (or on MN) such as the Mullins'.
A specific wrinkle is there is a gap between the threshold at which people cease to be eligible for JSA (able to work iiuc 40 hours a week in any job for which they may be qualified), and the threshold at which they become eligible for ESA (points based on being unable to do specific activities like walk 200 m, microwave a meal, etc).
To give an idea of recent changes, the old incapacity test awarded a gradient of points for being unable to go up stairs at all, being able to go up two steps, able to go up sideways, able to go up by resting halfway, etc.
The new test only recognises being unable to go up two steps. Anything else scores nul points. So a person who can do stairs slowly and only a few times a day will be scored the same as someone with no difficulties. They will be told to apply for JSA and then won't be eligible - or will go onto JSA only to be offered a job carrying boxes up and down stairs and have their JSA cut for refusing it.
This isn't a casual oversight. Someone sat down and thought about changing the existing test, and decided to do it.