If the case is still in its warranty period I would contact Samsonite. I had a similar thing happen and they sent out a full set of replacement swivel castors I replaced myself. They didn't ask for any proof of purchase - just asked for an address to post them out to.
That's the irony, the warranty say it's covered, but not for actual travel! Just remembering that 'The Checkout' on ABC exposed this too I think:
This warranty covers only manufacturing defects and does not cover any damage caused by misuse (such as transportation of unusual items), neglect, accidents, abrasion, exposure to extreme temperatures, solvents, acids, water, normal wear and tear or transport damage (by airlines for example).
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