Default help please....stock rom looping at M logo after factory reset

Got my moto g dual sim few days ago... And at that time it was working properly...but when i did a factory restore then it started looping at M logo, sometime only M keeps rippling and after that a blank screen appears. I tried restarting many times with no luck.After that i got it flashed by service centre. But i m still confused that how could factory reset cause this problem?? I m from india. Is it usual in moto g?? or anything else?? If anyone have idea please tell me..... Thanks

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