Hi Olivier,
Last week I had run into this same problem in that the pyferret package was built with one version of the NetCDF libraries, but the nco package was built with another. The problem is the netcdf library was updated in conda, but packages that depend on that library have all not yet updated to the same version. This is only a problem if both packages are installed in the same environment. And now there is a new version of the netcdf library, so the builds for all packages depending on that library (including pyferet and nco) need to be rebuilt.
I have started the process to get a rebuild of the pyferret package.
Best,
Karl