When DLA changed to PIP the one thing that altered was the automatic assumption that people with the same health condition had the same symptoms. My husband has Crohn’s and used to get DLA but he doesn’t qualify for PIP. They look at how the condition affects someone for the majority of the time, not worse day as it used to be.
Often it’s down to how people complete the form that makes a difference too. I’ve read claims were someone has written very little about how their condition affects them but submitted dozens of hospital appointment letters which don’t explain anything.
The other thing I have seen is a doctor letter which states ‘patient states they have backache’ rather than ‘I have diagnosed back ache due to a slipped disc’ for example.
I had something similar with an insurance claim when I was diagnosed with BC!
I am happy to help with anything you may be struggling with.