I've had a few bags of salt that I had stored in a cellar go bad on me. Was this just a random fluke or has anyone else seen it happen?

seen it atleast once before myself.

Huh... guess that bug is still around.

I wonder if setting salt's "spoil timer", or however spoilage is counted, if it were set to -1, would it spoil instantly/ever?

I think all food had a spoil time including spoiled stuff just set near the limit of a byte. Never tested to see how much of the stuff would eventually spoil but if the game doesn't check it might be possible to even have spoiled spoiled meat.

Or maybe spoiled meat becomes fresh again. :D