UC Query

Hi, my first time on a forum in many years and I'm just trying to find my feet at the moment, so please bear with me and I will try to keep it short!
...My husband [who works full time] and myself [disabled and receive H/R DLA] made a UC claim in Sept 2020 and a month later they asked for a Fit Note. My GP signed it with an 'Indefinite' end date and this was uploaded to my journal. I heard no more and we received payments every month. Occasionally we'd receive journal updates to log in and accept their 'commitments' or sanctions even though I've told them numerous times that I do not think I should be accepting them as i'm disabled and the rules simply don't apply to me etc. This year they paid a substantial amount into our bank account and my husband saw they hadn't taken his salary into account! Their error not ours!!...So messages on the journal and phone calls to rectify and we returned the 'Error' payment...this then led to several messages for me to upload a new Fit Note and that there was NO record of me ever having uploaded the one last October!! Despite me protesting very loudly in capitals on my journal and offering to re upload it, they were basically saying I was a liar until the lady that had originally dealt with the Fit Note, remembered and then said the reason it wasn't showing on my journal is that it is a GDPR issue so it was filed away and deleted! The current status is that I have now been referred for a Work Capability Assessment Questionnaire and I quote "It doesn't make sense for us to continue to ask for fit notes in this circumstance" ... Its now been two weeks and I've still not received it ... I have messaged my journal asking if they have a date that it was sent and no reply....but yet another accept commitmentments or face sanctions scenario.... This is all in a nutshell as trying to keep it short...I am so very very close to telling them to end the claim and having my sanity back, yet would be poorer. It is causing severe mental heath issues and I literally dread seeing I have another email from them!... My query is this... Should the Fit Note from last year have been dealt with sooner to prompt a Work Capability Assessment as it really does seem that they are ignoring my Gp stating Indefinte on the Fit Note. Many thanks in advance