I don't use the cases anymore but buy padded carriers with storage. You can spray with straight white vinegar for several weeks and always keep the top open. This works for old glue as well as mildew. Generally takes at least 2 weeks.
Generally, it is best to try it in spring or summer and sunshine after you spray. Leave on covered porch and spray several times a day. The smell WILL go away if you are regular and persistent.
PS Not hours in direct light but nice airy place with indirect sunshine. Outside is good bring inside late afternoon. I have 3 Featherweights bought for family members and worked on all. My 90 year old neighbor told me about method.
I dislike the cases as they bonk me and HURT to and from class so decided to buy small padded cooler on wheels with handle. Everything fits and no longer bruised up from case.
This is for your case only.