Preferences can reverse when nothing substantive changes. The switch is often caused by how options are presented or by which question you are answering.
Choosing an option is not the same as rejecting another. The mind can focus on different attributes depending on the task, producing different “best” answers.
Framing also creates reversals. A gain frame can make caution feel wise; a loss frame can make the same caution feel like surrender.
The fast system reacts to the most salient feature of the moment. The slow system can compare consistently, but it needs a stable criterion and time.
When you notice a reversal, do not assume your values changed. Often the question changed. To regain control, rewrite the problem in a neutral form and decide again.