I disagree that all prediction error equates to suffering. When you step into a warm shower you experience prediction error just as much as if you step into a cold shower, but I don’t think the initial experience of a warm shower contains any discomfort for most people, whereas I expect the cold shower usually does.
Furthermore, far more prediction error is experienced in life than suffering. Simply going for a walk leads to a continuous stream of prediction error, most of which people feel pretty neutral about.
On the other hand, the more you get accustomed to a pleasurable stimulus, the less pleasure you receive from it over time (hedonic adaptation). Since this happens to both positive and negative emotions, it seems to me that there is a kind of symmetry here. To me this suggests that decreasing prediction error results in more neutral emotional states rather than pleasant states.