Bad battery issues can be either, bad battery plugs, one of battery's elements is dead, you should introduce load to each element and veridy it'll hold around 2V. There's a tool for that.
Also acid density should be measured, volts alone do not tell the whole story, unless you measure battery output volts under load(driving, lifting or those two combined).

Also worty to check contactor, emergency kill switch pins for even voltage.

Abouy turtle stuff, you shoulf check screen, battery led display for error /event messgas. If it shows 19xx you can be quite sure there's error in safety equipment.