This is not uncommon.
Full dryness at night, can even still occur at this age.
You could ask the Pediatrician, to rule out anything.
But basically, our Doctor says that even at this age, they have accidents.
Night time dryness is a whole other process.
My daughter is 7. She still has occasional accidents. I just use a waterproof bed pad directly under her, and if she has an accident its not big deal. I just put a new bed pad under her, and I have about 4 of them so I can wash/rotate them.
I don't limit liquids or wake her just to go pee. She can do it herself. But sometimes she just sleeps SO deeply that she does not wake. Once she even had a dream that she WAS on the toilet until she felt herself wet. It was funny! And we laughed about it. She just gets up, washes herself off, then changes jammies and back to bed.
My daughter does not wear night diapers. But she still has accidents every blue moon. Normal.
My Hubby, did that too when he was a child.
All the best,
Susan