Not familiar with that charger, but does it have an on screen digital voltage reading display? If so, what was the voltage reading of the cells at the beginning/end of the charge cycle?
Most LiPo chargers won't charge if any cell is below 3.0V due to the following risk:
BU-702: How to Store Batteries ? Battery University
Originally Posted by Battery University
Li-ion cannot dip below 2V/cell for any length of time. Copper shunts form inside the cells that can lead to elevated self-discharge or a partial electrical short.
Some chargers have a safety cut-off timer to prevent over charging cells... it's possible that one cell might not be peaking properly and if that's the case then chances are the pack may need to be replaced.
Without knowing individual cell voltages, it will be hard to diagnose.