Exactly the same as you Lisa, was at processing stage but then went back to identity details received.
Just managed to get through on the phone 0300 330 0808 and they confirmed this a system glitch they are trying to address, and that lots of customers had been affected.
She assured me that the status was still at the processing stage (even though it wasn’t showing anymore).
I persuaded her to check my own application status and she confirmed that it was still processing (not at identity stage).
So fingers crossed, been 27 days since applied and supposed to be flying in 5 days!
Good luck
Mike