I think there is a bug with the `:cache' header and how results of
evaluation are wrapped: Using `:cache yes' and wrapping the results
prevents later blocks using the cached results.

To reproduce, start with an example like the one at the bottom of the
documentation in
<https://orgmode.org/manual/Evaluating-Code-Blocks.html>. Then add
something like `:wrap src R' (or `:results value drawer') to the header
of the block named `random' and the second block produces `nil' instead
of the desired result.

I verified the bug using `emacs -nw -q' with version 9.3 but would be
happy to send more information if the above is not enough to reproduce.

Thanks.