Follow the git log to see what encountering and resolving this issue looks like:

$ git log --oneline
6719385 (HEAD -> main) Fix conda-lock file by `rm conda-lock.yml && conda-lock`
ca3a030 `bump-my-version` is now on conda-forge! Remove `pip` section and re-lock
fa676c7 Initial commit with `pip` dependency

• Create an environment.yml file with a pip dependency, e.g. bump-my-version.
• Lock. Everything looks OK.
• Migrate that dependency out of the pip section, e.g. because that dependency became available on conda-forge, and change the version.
• Lock. There are now two copies of bump-my-version in conda-lock.yml
• Install from lockfile. The "old" version, which is no longer present in environment.yml, is installed. For me, this was very unexpected and took me a long time to understand why it was happening.
• Remove the conda-lock.yml file and lock again. Everything looks OK again.

📝 There is a corresponding bug in micromamba in which it will install the pip version but micromamba list will fib and tell me the version from conda-forge is installed.