I am trying to use <randomize> around a group of <problem>s inside a vertical to present different student with different problems. That part works fine.
However, when I use more than one <randomize> block I always get the same choice across all <randomize> blocks. In the above example one student might get A2, B2, C2 and another A1, B1, C1. This happens if I stuff those blocks into one vertical as shown above or if I keep them in separate <vertical>s inside one <sequential>.
My expectation was that I could also get problems such as A1, B2, C1 – essentially renewing the randomization of choice from one randomize block to the next