Yup I am noticing this bug now too, very annoying!
I have a possible theory how it happens, but haven't bothered to repeat the test to ensure: I noticed that the mushroom that it happened on was one that I had in the pot when the pot has only .1 L of water and so it never actually became "boiled" after the time was up (which I guess, is a whole other bug with boiling??). So then I had to refill pot to full and re-boil it and this was the shroom I ate that gave me poisoning.