We will never get again, I am in the same situation.
As I understand, persist partition content some certificate's of DRM L1, which cannot be recovered in anyway, persist partition flashed by us not contain that certificate's.
Certificate's are implement there only at the factory level.
Also, a similar persist partition taked from another DRM L1 phone will not work on our phones, there are different calibration of the sensors.
i have a persist partition taked from a L1 phone, maybe I will try to flash at a moment, but I don't want problems for now.
That's it, this happened when not reading with attention some informations before taking some actions like erase partitions on the phone, was getting in "Find device error internal memory corrupted", and I was found solution with reflashing persist partition, but information about permanently loose of DRM L1 wasn't there at that moment.