How to tune sensorless start-up of low inertia motor

I am using an STM32G431 running the ST motor control library for FOC sensorless control. My motor is running but the start-up performance is not satisfactory. I have about a 10% start failure. I have watched the YouTube video: Motor Control Part5 - 7 FOC with STM32 (STO, PLL, Cordic, MTPA, FW, FF) and they show a plot of Observer Elec Angle and Observer BEMF as shown here: Note the bemf amplitude is very clean and uniform, no modulation.

For my motor I think the low inertia could be a problem. The start current is about 500mA but the run current is only about 35mA. My similar profile of Observer Elec Angle and BEMF is shown here:

Note the ramp-up BEMF is modulated quite a bit. I think this leads to the high failure rate. I get MC_START_UP failures. I've tried tuning everything I can think of but can't find a good solution yet.

Can anyone give me some guidance on this?

Thanks,

Brian