How long are claims currently taking?

I applied for PIP in March. First I was sent a paper form to complete when I am allergic to the ink. Despite asking for it to be accessible I wasn’t offered a form by email. I had to put the letter in the shed until the chemicals off gassed before I could complete the form. It then took 10 days to arrive with them and be scanned making it late and rejected. I phoned to point out that they should have offered me an accessible format and after two more weeks they agreed to reopen my claim. I’m not sure if this counts as mandatory reconsideration.
I eventually got a face to face appointment at home in early August . I requested that the assessor wore no perfume/ aftershave or other chemicals due to my allergies. The assessment was hard going as she was wearing perfume making it very hard for me to concentrate and leaving me in considerable pain for a couple of days.
At least I thought that it would be worth it as my claim would now be considered. Last week I had a phone call from a hidden number claiming to be Capita, they wanted personal details which I refused to provide as I had no guarantee that I was talking to someone at Capita. Today I had another call, this time showing the number which I was able to look up as belonging to Capita. Apparently I need a reassessment as the assessor has left without completing the report and the computer had been wiped.
I asked what the timescale is for Capita completing an assessment and was told I should ask DWP as they set the timescales for each case. I then asked what the timescale is for my case and was reluctantly told 40 days.
Assuming that this is working days it should have been completed by mid September and yet I now have to go through the process again with no guarantee that the next person will complete the assessment or that it will be safe for me to let them Ito my home. I have no choice about redoing the assessment interview (well they did suggest they’d cancel my claim if I don’t)
Had anyone had anything similar? Also can I refuse entry to someone who will make me ill without me being penalised?
I am sending a complaint to Capita by email.