I made Sauerkraut a few weeks ago.
After about a week or so, I got to the desired sour/tartness I wanted, and placed it in the fridge.
I made a second batch, with similar results.
The problem I had , was one of the batches didn't have enough liquid in it, so some of the cabbage was above the liquid. I didn't realize it at the time ( or I would have submerged it), so when I took it out of the fridge to use it, not only did it look funky, but it smelled funky too. I just tossed it.
The first batch was fine, and is still in the fridge with no signs of decomposing.
Im guessing the cauliflower might have poked up above the water level, and the bacteria had a chance to get at it.