IMHO, the only ones "unpredictable" in Op.3/2 is the
Agitato section.

This may sound arrogant but when I studied Op.3/2 years ago, I memorized the first and last sections (main themes) - except the
Agitato part - in one sitting! Since then, I merely have concentrated polishing only that fast middle portion.
Op.118/2 is more unpredictable as I see it. As in other Brahms
Intermezzos, there's no stable chord pattern. And I still haven't memorized it

!