The opam archive for version 4.0.0 seems to have changed

[mseri]

From https://opam.ci.ocaml.org/github/ocaml/opam-repository/commit/530f075fbfd6646cef636cefe0a5a5eaaf26135a/variant/compilers,4.11,cohttp.4.0.0,revdeps,KaSim.4.0.0

[ERROR] The sources of the following couldn't be obtained, aborting:
          - KaSim.4.0.0:
            https://github.com/Kappa-Dev/KaSim/archive/v4.0.tar.gz (Bad checksum, expected md5=894a517c7991f42100d2e957efc6cfa2)

You can recover the original archive from https://opam.ocaml.org/cache/md5/89/894a517c7991f42100d2e957efc6cfa2
Could you replace the tarball of the v4.0 release with the old one from that URL?

[mseri]

The same issue appeared for 4.1.0:

[ERROR] The sources of the following couldn't be obtained, aborting:
          - kappa-agents.4.1.0:
            https://github.com/Kappa-Dev/KappaTools/archive/v4.1.tar.gz (Bad checksum, expected sha256=f24a38f73a88f1b3d8137aa083bad8d76c679c4b6c59ec29e1567ad95bf1df13)
          - kappa-binaries.4.1.0:
            https://github.com/Kappa-Dev/KappaTools/archive/v4.1.tar.gz (Bad checksum, expected sha256=f24a38f73a88f1b3d8137aa083bad8d76c679c4b6c59ec29e1567ad95bf1df13)
          - kappa-library.4.1.0:
            https://github.com/Kappa-Dev/KappaTools/archive/v4.1.tar.gz (Bad checksum, expected sha256=f24a38f73a88f1b3d8137aa083bad8d76c679c4b6c59ec29e1567ad95bf1df13)
          - kappa-server.4.1.0:
            https://github.com/Kappa-Dev/KappaTools/archive/v4.1.tar.gz (Bad checksum, expected sha256=f24a38f73a88f1b3d8137aa083bad8d76c679c4b6c59ec29e1567ad95bf1df13)