An easy-to-imagine scenario is that a router with multiple egress paths emits the UDP packet on multiple interfaces. The packets take different routes but both arrive at the destination.
With multiple egress paths different packets from the same stream can be sent using different routes and arrive to the destination at different order but each packet should be delivered at most once. Unless there is a bug in the router which duplicates packet - possible in theory but in 20+ year practice I haven't see one. This is not to say routers are bug free, just this exact problem is not what I would expect.
