Huh. Dish soap.
My contact said that although the employees asked why there was going to be a shortage of dishwashing liquid, no explanation whatsoever was provided.
I'm personally not sure why this, of all products, should fall short, but it would be a good idea to pick some up. You can order a couple of jumbo jugs of Dawn or 4 bottles of Palmolive, and Amazon isn't showing any messages to say "only 3 left, order soon." But if everything is fine with the dish soap supply, you won't have spent a lot of money on some otherwise useless item. Dish soap isn't an expensive item and it's not like you won't use it up.
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Despite that, if Walmart is putting out such an oddly specific alert to employees, I would suggest stocking up either on Amazon or at your local stores. It also might make one curious whether we'll soon see shortages of other cleaning supplies, as many ingredients would probably be the same.