Hello Gad,
The ESC gradual error increase means that the hardware current limit is reached. I.e. the motor phase permanent currents esceded 60 Amps. In the voltage control mode the current loop is not used. That’s why it’s impossible to limit the phase currents in the software. But you can limit the max motor current in the software if you switch to the rpm control mode. You can find the tuning recommendations in this post.