(I think) directories listed in ./_tags files ingested by ocamlbuild are not sorted, leading to (eg.) "-Ifoo -Ibar" vs "-Ibar -Ifoo" and a corresponding (un)ordering in the ocaml load path as revealed by ocamlobjinfo. See, for instance src:ocaml-uunf
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).