Hi and welcome to Just answer.
Initially, Bm error means that stepper motor is not properly initialized. The problem is commonly the electronic control board that control the movement of stepper motor.
For our initial fix, we will try to reset the electronic components of your board. Unplug your machine at least 2 hours then plug in and power on your machine.
If this doesn't work, I'd take it to a dealer for repair (they might well have a loaner for you) -- the stepper motor initialization error says that one of the little motors controlling needle position hasn't got a clue about what to do, which is often a board fault.
Let me know if you still have questions.
Hope this information will be helpful.
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