iPhone 5s has a few very small components right aside the battery connector, in the small space between the connector and the metal shield. I’ve seen quite a few times components lifted away or solder joints damaged by mistake when removing the connector and this might be case too. You’ll need a good light source and good magnification to see capacitors and resistors and gently check if they are solidly in place or they slightly move about. You might find empty shiny solder joints too, give it a check.