Actually the last ditch solution which seems to have the phone working again at least for another few weeks so far using the new battery, this was to pop the phone into the freezer for 5-10 minutes.
Only explanation I can think of is that would explain this as a more than temporary solution is that.
within design it possible to include snags that prevent a contracted metal from expanding again when the temperature increases again, it would be a very efficient way to sealing a contract point, but it is not something I have ever hear of before, but this is not my field
Note if others use the freezer method , the phone should be wrapped in cling film and maybe tin foil, to prevent possible damage from moisture ingress. After a test period in the freezer the cling film should be left in place until the phone returns to room temperature again, this would help prevent moisture ingress,
and possible internal moisture condensation within the phone. Neither of which are good for any electrical circuit.
I had previously read about cooling a phone in the fridge before. It is not an uncommon solution for hard drives. But the same phone continues to forget that it contains a sim card every now and again which means I am on the look out but less urgently looking for a new phone, maybe the Ellephone M2 , I am concerned that that company has had battery issues with a number of its previous models .