Agree w the Clorox and water mix remedy. 6 yrs ago I purchased one of my FWs in an estate sale. The case had an intolerable moldy smell. I was tempted to trash it. A plumber suggested I use bleach w water in a spray bottle and lightly spray (like a mist) and to fan dry it 6-8 hours. Told me to repeat that until mold was eliminated.. Sprayed and fan dried for 3 days. It did clear mold and smell.
I store the case in my hall closet w top open.