CONTACTS in iPhone 10s has 26,000 copies of one entry. NOT showing in iCloud Contact

My iPhone XS is on 18.6.2 and is well looked after. But behaving weirdly now… For example, it keeps turning on driving mode when I'm standing at my house on the phone. Sometimes it can't load webpages or apps ....just a blank screen pause. it's at 371GB out of 512GB.

I was looking through my contacts and noticed that it has created contact lists itself, e.g. For each of my email addresses, it has collected contacts from the main list and put them in there.

The newest email address has copied and re-copied one particular contact (it's just an email address to my bank, a particular department that discharges mortgages, which I used once two months ago I didn't have the address before that). Now has 26,000 copies of this one address.

I don't want to delete the one by one. But I can't delete the whole list itself.

The main phone contact list has synced normally to iCloud, the rogue email list has not synced with the iCloud so I can't edit it there.

Really just deleting the whole list in the phone contact itself would be fine, but every time I click on EDIT at the top of the main contacts screen, it just says "Done"

Any solutions?