Is it normal for the dreads on the nape of the neck to unravel quickly and take longer to lock up?

I'm black and have had my dreads for 5 months most of my hair is in the budding stage but the back constantly unravels and won't lock up as of yet. I started it when my hair was really short i dont use beeswax because it leaves gunk in your hair. Any help would be much appreciated.
Is it normal for the dreads on the nape of the neck to unravel quickly and take longer to lock up?
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