How old are the batteries and how many normal charge/discharge cycles have they had so far?
Have they been unused for a long period of time? If so, would they have been charged occasionally during storage?
As you have been able to measure the wattage, are you also able to see the battery voltage just before it cuts out as well?
Alternatively, if you are reading the wattage from the BAC-601 Smart Display, do the five bars in the battery capacity gauge disappear completely just before it cuts out?
Do you have to turn the battery off and on again to make it work again or does it reset itself automatically?
I don't know if the bottle batteries use the same connection for charging and power output or whether it might be possible to test the battery voltage at the charging port during use to see how much it drops under load.
It will be interesting to see if the overnight charge has had any effect on "blinking between green and red", and also the cutting out.
Alan