Frank, Your battery may be fine but just the BMS is out of sync. You need to try taking it down, but the "down to 8%" is WRONG: depending on how far out of sync the BMS is, going down to 8% MAY fix it, but no guarantee.
The correct wording should have been "take it down to 7%." I think it was typical Chinese manual language conversion error.
Small change, but proved many times. What often happens is it will get to 8% but then folks shut it off - but but but that is where it often BEGINS the recalibration! So it will stay at 8% value whiile the battery voltage continues to drop to the calibration point (IIRC 3.7v avg/cell).
So do as you suggest, or better yet, just plug it into assistance and watch % charge and actual battery voltage.... from your description you will see it hit 8% charge yet the voltage will be way higher than 3,7*3=11.1v... watch in amazement when calibration kicks in... 8% will remain but voltage will continue down - UNTIL t hits 6-7% at around 11.0-11.1 volts! NOW it is calibrated. Shut it off and go recharge and fly.
Or do both; assuming you have fully charged battery in reality, fly it down safely, then put on assitant. assistant draws 1 amp while running, so it would take 5 hours to discharge a fully charged batt on assistant alone.
If you want to see more of the science behind this, go here:
Let's start posting dji assistant BATTERY data, HERE!