Sphinx might output references to memory addresses and generate a json index file with entries in random order or with non-deterministic values (eg. searchindex.js). See https://bugs.debian.org/822197 for memory address issue . searchindex.js needs sort_keys=True (jsonimpl.py) but the key values vary too.
Sphinx can output genindex.html index entries in non-deterministic order. . There might be other missing sorts or dict key sorting beyond the pull request already sent.
Our notes about issues affecting packages are stored in notes.git and are targeted at packages in Debian in 'unstable/amd64' (unless they say otherwise).