Details for "make inconsistent assumptions over interface Seq" error

Is there any way to get more details about what actually went wrong for errors like this?

ocaml-calendar, native build with clean ocaml 4.05/6 based tree:

[   52s] Command [21] exited with code 2:
[   52s] $ (cd _build/default && /usr/bin/ocamlc.opt -w -40 -g -bin-annot -I tests/.test.eobjs/byte -I /usr/lib64/ocaml/alcotest -I /usr/lib64/ocaml/astring -I /usr/lib64/ocaml/cmdliner -I /usr/lib64/ocaml/fmt -I /usr/lib64/ocaml/fmt/cli -I /usr/lib64/ocaml/fmt/tty -I /usr/lib64/ocaml/re -I /usr/lib64/ocaml/result -I /usr/lib64/ocaml/seq -I /usr/lib64/ocaml/stdlib-shims -I /usr/lib64/ocaml/uuidm -I src/.calendarLib.objs/byte -I src/.calendarLib.objs/native -no-alias-deps -o tests/.test.eobjs/byte/test_printer.cmo -c -impl tests/
[   52s] File "tests/", line 1:
[   52s] Error: The files src/.calendarLib.objs/byte/calendarLib__Printer.cmi
[   52s]        and /usr/lib64/ocaml/alcotest/alcotest.cmi
[   52s]        make inconsistent assumptions over interface Seq

ocaml-mdx, native build with clean ocaml 4.05/6 based tree:

[   53s] Command [86] exited with code 2:
[   53s] $ (cd _build/default && /usr/bin/ocamlc.opt -w -40 -g -bin-annot -I lib/.mdx.objs/byte -I /usr/lib64/ocaml/astring -I /usr/lib64/ocaml/compiler-libs -I /usr/lib64/ocaml/fmt -I /usr/lib64/ocaml/logs -I /usr/lib64/ocaml/ocaml-migrate-parsetree -I /usr/lib64/ocaml/ocaml-version -I /usr/lib64/ocaml/ppx_derivers -I /usr/lib64/ocaml/re -I /usr/lib64/ocaml/result -I /usr/lib64/ocaml/seq -I /usr/lib64/ocaml/stdlib-shims -no-alias-deps -open Mdx__ -o lib/.mdx.objs/byte/mdx.cmi -c -intf lib/mdx.pp.mli)
[   53s] File "lib/mdx.pp.mli", line 1:
[   53s] Error: The files lib/.mdx.objs/byte/mdx__Block.cmi
[   53s]        and /usr/lib64/ocaml/re/re.cmi make inconsistent assumptions
[   53s]        over interface Seq

The same set of sources throw no error in clean ocaml 4.07/08/09 based trees.

Another one from tyxml and ocaml-4.05:

[   56s] Command [17] exited with code 2:
[   56s] $ (cd _build/default && /usr/bin/ocamlopt.opt -w -40 -g -o test/test_html.exe -I /usr/lib64/ocaml/alcotest -I /usr/lib64/ocaml/astring -I /usr/lib64/ocaml/cmdliner -I /usr/lib64/ocaml/fmt -I /usr/lib64/ocaml/fmt/cli -I /usr/lib64/ocaml/fmt/tty -I /usr/lib64/ocaml/re -I /usr/lib64/ocaml/result -I /usr/lib64/ocaml/seq -I /usr/lib64/ocaml/stdlib-shims -I /usr/lib64/ocaml/uuidm -I /usr/lib64/ocaml/uutf -I implem -I lib /usr/lib64/ocaml/uutf/uutf.cmxa /usr/lib64/ocaml/seq/seq.cmxa /usr/lib64/ocaml/re/re.cmxa lib/tyxml_f.cmxa implem/tyxml.cmxa /usr/lib64/ocaml/result/result.cmxa /usr/lib64/ocaml/stdlib-shims/stdlib_shims.cmxa /usr/lib64/ocaml/fmt/fmt.cmxa /usr/lib64/ocaml/astring/astring.cmxa /usr/lib64/ocaml/cmdliner/cmdliner.cmxa /usr/lib64/ocaml/fmt/cli/fmt_cli.cmxa /usr/lib64/ocaml/unix.cmxa /usr/lib64/ocaml/fmt/tty/fmt_tty.cmxa /usr/lib64/ocaml/uuidm/uuidm.cmxa /usr/lib64/ocaml/alcotest/alcotest.cmxa test/.test_html.eobjs/native/test_html.cmx)
[   56s] File "_none_", line 1:
[   56s] Error: Files /usr/lib64/ocaml/stdlib-shims/stdlib_shims.cmxa
[   56s]        and /usr/lib64/ocaml/seq/seq.cmxa both define a module named Seq

Well, of course they do. Why is this a problem only for a tiny subset of the packages?