It happens with toxins, which is the reason why cooking spoiled food isn't a magical solution to everything.
Examples are on-living molecules whether inorganic simple elements or complex thermo resistant proteins leftover from other forms of life like fungi.
That said, there's nothing special in a forever stew that makes it particularly more susceptible to this risk. The toxins don't reproduce (unless there's some fucky crystallization phenomenon, but that's sci fi speculation), and if there is some thermoresistant toxin introduced, then it will probably be dilluted quickly.
I highly doubt a perpetual stew would be at boiling temps, the stew would disappear too quickly. I would think it'd be at slow cooker temperatures, 80 - 90C. High enough to kill off the nasties but low enough to not be boiling.
Examples are on-living molecules whether inorganic simple elements or complex thermo resistant proteins leftover from other forms of life like fungi.
That said, there's nothing special in a forever stew that makes it particularly more susceptible to this risk. The toxins don't reproduce (unless there's some fucky crystallization phenomenon, but that's sci fi speculation), and if there is some thermoresistant toxin introduced, then it will probably be dilluted quickly.