Additionally, I also faced another issue with the new firmware: there were lots of hiccups at low speed and sometimes motor even refused to start.
It turned out to come from "Hall stall fall time" that was cutting power off, I changed it from 10 to 100ms and everything went fine.
I don't clearly understand why previous firmware wasn't faulting with a stall fall time of 10ms, whenever I didn't changed any parameters...
U used this controller for some time, so i suppose the motor's basic parameters & hall sector are set up exactly;
Then i think u should be focus on current regulator Kp & Ki, Speed regulator Kp & Ki and PLL Kp & Ki;
If there was some noise & resonance in low speed,u can try to decrease current regulator Kp & Ki value;
If there happened hiccup when start, or full throttle start, or in the process of acceleration, it's most likely due to bad setup of PLL Kp & Ki;
for you case, i will suggest PLL Kp=1000, Ki=1, maybe this is a way to solve your issue.