If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.
1.) How does the external power supply respond to a load step do you see any instability overshoot.
2.) How long are the leads from external power supply to charger, the leads will act as an inductor and starting and stopping current flow will cause a voltage kick/overshoot.
3.) Input filtering into charger, how large is it will adding more capacitance help reduce any possible overshoot.
4.) Try measuring voltage at the BQ2057 VCC looking for overshoot during plug/unplug.
