Mental health and pip

Hi
Looking for some help for my brother who is 61 and suffers with schizophrenia since his 20’s.
He was on an indefinite award of DLA and in July 2019 he received a letter from the local benefits office saying that someone was coming to visit him to help him fill in his pip form. At the time my brother was extremely unwell and had withdrawn himself from everyone and not taking any medication. He then called DWP as he was paranoid and delusional and told them he did not want to claim DLA or PIP as he was no longer disabled !!!
The very same day his mental health team gained entry and he was sectioned under the mental health act. Now he is better and on medication he agreed to re apply for pip so we sent the forms in explaining the situation and asked for paper based as anything else would be detrimental to his mental health.
Independent services have had his form since 16th December 2020 and despite me calling to see how long they said due to back log his has not been looked at yet !! Is this because of covid or because we asked for a paper based assessment !
Also when he cancelled DLA he was in aware he was receiving a disability premium with his ESA and they have contacted him a year later saying he should not have been claiming this and they are stopping £25 per week from his ESA as he owes £2750 how do we stand with this should I appeal this for him or wait until his award has been reassessed ?
It’s so frustrating I wish DWP would have thought that surely if someone with MH issues who has been on DLA for years cancels their benefit then alarm bells would ring
Any help would be appreciated as I’m not sure what to do
Thank you