BLDC motor intermittent start-up

Hello to all experts. My first post here.

Hope this is the right place for this question.

I have a 3-phase BLDC motor (as part of a cordless screwdriver) with 3 hall sensors (type J55 eD) inside.

SOMETIMES, when pressing the main switch, the motor does not start, and the only way to get it started is to disconnect the battery pack and reconnect it again; then the motor works normally again until the next failure which could be in the next hour or the next day.

Any idea why this is happening? Can someone give me a hint as where to look for the reason ? Is it the motor hall sensor, the drive electronics … ?

Thank you, in advance.

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