Hey. I am facing the same issue. I have a QS138 V3 and a Sabvoton 72150, and after I hit that peak, the motor almost locks up, I also have the stalling issue when I go from a standstill, where I have to give it a little push to go. Just to let you know, this is not a battery issue. I built my own battery using brand new Lg HE4 power cells. Based on my configuration, this would not be an issue of current, since the battery can handle over 350 amps. I also am running unprotected, only using my BMS to charge the battery. I have leads coming into the controller directly from the battery. I would really appreciate it if any sabvoton expert would have any ideas on how to solve this, because it is honestly very dangerous. When I am doing a high-speed pull and the wheel locks up, there's a 90% chance I'm not gonna be on that bike for a while... When this happens, I also have to fully stop the bike, then turn it off, and turn it back on. I was thinking of unlocking my controller using the unlock software (https://archive.org/details/mqcon-current-unlock). If I were you, I would mess around with the software, motor poles, current limits, and phase limits.
Best regards, Ivan.