Council Tax exemption

Hi, I’m hoping someone can help me understand how Council Tax Reduction works when you have an adult disabled son living with you.
I’m currently on Universal Credit and have been receiving full Council Tax Reduction. I’m also my son’s carer and I’m currently awaiting a PIP assessment myself. I have ADHD, EUPD, PMDD, Raynaud’s, sciatica, tinnitus, insomnia and ongoing joint problems.
My son, Zachariah, has Cystic Fibrosis and ADHD. He was previously in education and had an EHCP, but unfortunately he was removed from college and is no longer attending.
He is now classed as a non-dependant because of his age. He receives Universal Credit in his own right and receives the enhanced rate of PIP for both Daily Living and Mobility. He has also been signed off as not fit for work by his doctor and is currently providing fit notes while waiting for his Work Capability Assessment to determine whether he has Limited Capability for Work/Work-Related Activity.
The council are now saying that because he is a non-dependant, an amount needs to be deducted from my Council Tax Reduction because he is expected to contribute towards the Council Tax.
What I’m struggling to understand is whether a non-dependant deduction should actually apply in our circumstances, particularly because Zachariah receives enhanced PIP, is currently medically signed off from work and is awaiting his Work Capability Assessment.
Does anyone know whether I should still be entitled to full Council Tax Reduction, or whether I genuinely have to pay an amount because my son is now classed as a non-dependant?
If anyone has been in a similar situation, particularly with an adult disabled child receiving PIP and Universal Credit, I’d really appreciate hearing how your council dealt with it.
Thank you!