Randalls warranty is excellent. I assume the handle will be replaced. Repairing a crack so its unnoticeable is too painstaking. Ive never heard of any manufacturer repairing handles, they usually replace them. Some private craftsmen fill the cracks with the epoxy , matching the color. Its a very tedious task and does not guarantee that the handle will not crack again

A friend of mine had a Sambar horn (not a Randall, Puma Nicker) crack when he flew on a plane to the desert in winter. He lived in the north near the sea. I think it was caused by the sudden change in humidity and temperature - from 0 C to +45 C, and from high humidity to near zero. Puma just replaced the handle