I have used the following to remove odor and the damp smell from several lined case:
1, Vac any loose stuff .... get in all the corners.
2, Using a mix of liquid laundry detergent and color safe bleach, lightly sponge the interior .... blot dark spots .... then with a well squeezed spunge and clear water ... blot away the cleaner solution ..... it will take a few reps to get the suds out.
3,Set it someplace to dry ..... in the sun is fast and helps the process.
4,When it is bone dry I like to fill it with cedar chips, close it up and leave it for a few days..... or dump a box of baking soda in a shallow container and leave that for few days.
This has worked for me several times.
Note: If mold between the lining and the shell, nothing will get it out ..... relining is the only option.
Hope this helps
Al