Cornmeal won’t set up I feel this is violating at least one law of physics.  I’ve tried twice now to make polenta recently.  All my life it’s worked as expected.  But these last two times the cornmeal starts to setup within a few minutes of stirring, then progressively begins to reverse course until it’s just water and some grit at the bottom.

The cornmeal was bought about a month ago.

Does anyone have an explanation for what can cause this?
It sounds like maybe you have introduced an enzyme (such as alpha amylase) into your polenta. What is in your recipe? You might try cooking your polenta at a boil for at least 30 seconds.