First thing to note is anytime the vehicle shuts down due to say an error and then powers back up the state of charge will reset to 50%. So, my assumption is that an error is being produced at the end of the charge cycle. This can happen when the amperage reading is off. So basically, the amperage is reading -1/2 amp but charger is off, so this reading needs to be 0.
The operator is unplugging the vehicle which when error is present will shut down the vehicle resulting in error being removed. Then plugging it back in and charger starts up, but vehicle is fully charged to state of charge increases to 100% rapidly.
A simple way to check the amperage is the digital dash display has a second screen providing battery information. With key on press and hold up button until second screen comes up. Should be just a few seconds. In there is "Pack Current". With key on this should be reading 7/10 (.7) amps. Also note that it is a positive reading. (Not -.7). If this is off take and be next to an area you can plug in vehicle. Turn main battery disconnect switch in the front right wheel well to the off position and then turn back on. Then plug in the vehicle like you're going to charge it just until the vehicle powers back on. Then turn ignition key on and check the amperage reading again. Sometimes powering it up while being plugged in can cause amperage to zero incorrectly.
Another thing you can do is to unplug and plug back in the current sensor. I have seen where a bad connection at the sensor can cause an issue. The current sensor is located on the negative battery cable just off the B- of the main battery pack. The current sensor looks similar to U5679A-N.
If some other error is in the system this can be checked by having the issue happen. Leave the vehicle plugged in and connect to the vehicle with a computer using this tool part# U5665A-N to see what fault is triggering. Here is a link to a forum explaining how to check for trouble codes.