When they install them they very often, too often over tighten the hold down clamps, reuse old rusty one or small cheap ones and they can cut into or crack the case even if very small cracks. If your leak is around the post replace it or all of the batteries or if it is leaking from where the clamp is or anywhere else.
Over heating the battery such as if they go dry and you refill and charge or desulfate, them and the clamps are too tight it may leak there or elsewhere.
Not much of any way to repair the case but..I don't know everything.