My recent PIP tribunal has left me a little confused, I’m wondering if anyone have had this happen.

I won my original tribunal in August 2015, I received a letter stating I needed to start a new claim as this would run out January 2019.
I did what needed to be done, I was assessed and my enhanced on both care and mobility went to standard care from April 2018 - August 2022.

My recent tribunal was a matter of sat down with two Doctors and a judge. To be told, DWP had made an error as they had failed to prove that my health conditions had improved.
They allowed for any money’s owing from April, although I will have to make a fresh claim, as any further health conditions I’ve incurred since April 2018 are not included in my claim for PIP. ( I has been either waiting for appointments or results before I could change my circumstances.

I assume DWP should have allowed my original tribunal win, until January 2019, but were a little premature in allowing the fresh claim to take over ?????