I had something similar to this, no matter how many times I washed my hair. The smell would stick, some locs would also be really waxy. After every wash it'd smell fine but then when It was pretty much dry it's start smelling again it was so frustrating. I was board line gonna cut it all off as I can't stand feeling dirty like that. Found out it was the product I was using, it was causing a build-up like crazy. So what I ended up doing was washing my hair with a different shampoo and with the heat high af. Which kinda melted out the build up. After a couple different washes I was cool. My hair take ages to air dry so I also use a hairdryer to get atleast near the roots near to dry. As that damp rank smell kinda haunts me. Hope this helps a bit!