7.2 volts is too low of a storage voltage for a 2S, at least for an extended time. The pack was essentially fully discharged, not much margin for error/slight self discharge.
A typical resting voltage vs capacity table, based on discharging at 1C to 3V. Of course this will vary some by cell but most tests I have seen over the years are fairly close.
4.20v = 100%
4.03v = 76%
3.86v = 52%
3.83v = 42%
3.79v = 30%
3.70v = 11%
3.6?v = 0%
3.8 to 3.85V per cell, or 7.6 to 7.7V for a 2S, is a much more reliable storage voltage best I can tell.