if you have a Curtis handset, you can plug it into the controller in the wav, it will tell you the error in whatever language the handset is setup for
my bet, without looking up the codes, but knowing wavs somewhat, is that this code refers to one of the motors having bad brushes,
On their best days in the best operations, it seems the 1st generation of wav motors were not what anyone would consider to be 'heavy duty' or 'long life', I am withholding judgement on the second gen wav motors.
My recommendation is that you pull both drive motors and check the brushes and blow out the carbon dust. I am pretty sure Crown suggests this for each PM.
my bet is that it is the left drive motor. (we in the USA, turn right more often and that means there are more times when the right [inside] drive motor is turning less and the left [outside] motor is pulling more amps)

Thanks 1Crusader. I will give it a go. The batteries did read over 6V each, total 25.4V

Wow, Checked all my books and notes and could not find a code 70 or any close to 01000110. Start with all the simple things first.
1 check and charge the batteries first, you can use an automotive charger 12 volts doing one side of the truck at a time. After a few hours on each side try the on-board truck charger.
If the light bar on the furthest left is flashing you may be having a problem with the communication board but I would check everything else first.