The battery was very old and the current provided by the old battery was not powerful enough to sustain normal operation of the phone after a certain amount of battery life had been depleted.
The repair went by easy, although I lost the little metal piece that kept the camera in place I used electric tape to hold it in its position instead. Unfortunately I may have damaged the vibration motor as that function is not working any more and maybe the bluetooth as well. So, it is not the last repair I will have to perform.
It is better not to work near a table edge as parts may fall and disappear into instantaneous wormholes.