Too true. It could be a not-fully-plugged-in plug, it could be a bad charger chip, it could be another problem on the motherboard. That's why we always try to discourage people who aren't trained cellphone techs from doing D-I-Y repairs. It's not that we want to make the repair shops rich, but we don't want people wasting time and money replacing something that a) doesn't need to be replaced and b) won't solve the problem, and we don't want people to damage their phones. Even with years of experience, I no longer do "inside" repairs - I no longer have my test equipment (a good 'scope, to start) and at 77, my hands are no longer that steady - so I have an S5 with a bad charging port that I don't want to pay $90 to get replaced, so I use a $3 external battery charger.