A couple of days ago, I loaded up several stoves in my world each with1 stack (64 blocks) of cobblestone and 8 charcoal. Did some other things that I can't remember exactly. (I may have entered the nether while the stoves were cooking, then exited the nether and then saved and exited from the overworld and changed the difficulty all very quickly, since I never save while in the nether). The quick save and exit as the stoves should have been restarting may have prevented the stove info from properly reloading after i left the nether.)
Today, I entered that world (resetting the nether in the process) and all the stoves were off with only about half of each stack of cobblestone cooked and with NO fuel left in any of the stoves. The amount of cooked cobblestone does vary by a block or two which would be consistent with a shut down of the process at a single instant (i.e. with the variance being due to the time it takes to load each stove individually). So, basically, somehow the game has just lost the 3 or 4 charcoal that should have been in each stove when whatever I did shut down the cooking process and the absence of the fuel is what has prevented the stoves from just restarting the cooking process when I re-entered the world today.
BTW, this is a single-player offline world and no one else in the household has been around this past week to be playing a prank on me.