Depending on the banana plug, the hosing is usually insulated, even if metallic (usually a coated aluminum).
Of course you could wrap with electrical tape of coat with a non-conductive materiel.
I think one of the most important things to keep in mind with all connectors, is the question your post raises:
How did contact happen? Are your cords to short or heavy thus pulling and/or bending the terminals?
I use bananas and make certain that there is no stress on the cables. Even with all that packed in to a relatively tight space, I am not worried as I have made certain that there is minimal risk in cabling getting tugged or the binding posts bending.
Of course, it should go without saying, if you are going to mess with connections in any way: turn it off first!
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