48v problems

Hello guys

i built a ride on car powered by vesc 6.6 dual plus from flipsky and 6374 motors. it is fully remote controlled and manual controlled at the same time . I managed to have remote control over the disk brakes, throttle and searing. the car at 24v clocked 30km/h. 

It is probably the most complex usage of the vesc. I used all options possible. The car has now 

•  a full working dashboard
• complete car light (signals, low beam and high beam, brake lights)
•  front brake discs
•  servo controlled brake and throttle pedals
• servo controlled steering and reverse switch
• powered by 4 6s batteries with 14000mah each

this is my channel if you what to check it out   https://www.youtube.com/playlist?list=PLUMGsXqyC7-oguhZewHxejr_i5Qj9gVu5

the car worked perfect at 24v after months of modifications and programing

when i upgraded to 48v i started having different problems

1 duty cycle doesn't work properly afte50% the motors start to vibrate and the vesc resets. some times i can see over voltage fault

I use the car in current mode. and managed to clock 52km/h. it will go 60km/h

2 when i power on the car and start using it for about 3 times when i push the pedal the vesc resets . after that it runs normally

3 the throttle is more aggressive even with -50% throttle curve. it sis very difficult to use at very low speeds. especially when i drive my son remotely

I didn't have this problems at 24v

Please let me know if you guys have any solutions

Thank you