most of the braking power is from the regeneration it might brake weird if 12volt battery is bad (i.e bad ground cable )
my ground cable is bad as well.. i got a replacement (before the price skyrocketed ) the engine would stall out while braking to a stop,
i know the HV battery is bad but after messing with the 12v ground cable it was much better..
make sure the voltage is reading at lest 14.5 to 14.9volts at the terminals if it's less then that
then you got a bad connection... and you're going to have a bad time
also have the 12v load tested
i still haven't put the new cable as i can't get the old one off
it's on there good