I have had same “battery deep discharge” problems on various gadgets. I solved some case with follow instructions:
Try to load you gadget to plug charger on and off multiple times. Everytime you plug charger to gadget some power goes to battery and then protection circuit is acting up. I think that reason is that there is no power and protection circuit is not working for that reason. When you plug on and off charger multiple time there is change that there is finally some power on battery and protection circuit come to life.
I use power timer for this. 1 min on and 1 min off..
Another way to bring your battery to life is the following trick which applies to many deep-unloaded tablets/phones.
Keep the power button pressed with a piece of tape and something hard under it. Now put it on the charger for an hour. This will bypass the circuit and charge the battery. Don’t keep it too long because it may damage the battery.
Now unplug the charger and remove the tape. The tablet powers on as normally, and you can charge as normally now.
.
.