PIP Mobility 11f

My son has had enhanced rate mobility for his autism and having to be accompanied. He was last granted enhanced rate at a tribunal in 2020. We had a "light" review in July where I said nothing had changed. They said they had tried to ring me to ask me some questions but I had no phone call. I then had a telephone assessment where I clearly stated that he has to be accompanied to his part time job by a co-worker even though he has had psychological issues with bereavement of his two brothers within two years. I do not understand why, again, they have only given him the standard rate (11e) when I said he goes out three to five days sometimes more depending on the part time work.

I requested a mandatory reconsideration but it has come back the same "In our original decision we accepted that you need help with preparing food, eating and drinking, managing treatments, washing and bathing, dressing and undressing reading, mixing with other people, making budgeting decisions and planning and following (a) journey. We have reviewed the evidence including the assessment report ..... are unable to increase your award of Personal Independence Payment."

I am appealing against this decision. What case law can I apply in this case? I would really appreciate some help as I myself am suffering from PTSD due to both my sons dying within two years of each other.