Kids, have accidents.
No child, is 100% accurate.
Night time dryness and/or nap dryness, is not something biologically attained, until even 7 years old. And this is normal.
It is about the body's physiological/brain and nerve development.
My daughter was 5, and still in night time diapers. Normal.
My son is 4 and still in night time diapers. And for naps.
Even if they were/are potty trained already.
Normal.
But they still have accidents at night.
My daughter, had accidents during the day time too....
IN fact, ALL of her Teachers- Preschool, Kindergarten and 1st Grade, said that kids these ages, DO have accidents. Normal.
They are young.
Kids, at this age, 'think' they can hold their bladder longer than they can. But they can't. Or they get distracted. Or don't want to stop playing just to pee. It happens at about 3-4 years old.
It is a learning curve, still, about pottying.
Even if they know 'mentally' about pottying.
Their body/biology, is still developing.
Kids have accidents.
It will happen.
It is not 100% accident free.
Even if they are potty trained.