A post on social media site Reddit that was shared just after Thanksgiving has kicked off a widespread online debate about a kitchen staple from Costco, one of the largest big-box retailers in the U.S.

Costco devotees are complaining that their preferred retailer's own brand of butter is suddenly causing their baked creations to fall apart, leading them to speculate that it changed the formulation of its Kirkland Signature "blue box" sweet cream butter.

To be considered butter, cream products must meet a federal standard, set by the U.S. Department of Agriculture. It must be made exclusively from milk or cream, or both, and contain at least 80% milkfat. A package of four, one-pound boxes of Kirkland butter costs about $17.40, according to Instacart. That's considerably less expensive than Land O'Lakes butter sold at Walmart, for which an equivalent amount would set you back about $24. But some bakers say they're switching allegiances after encountering problems while baking with the Kirkland-brand butter.