Ionic, npm and yarn

Some time ago I had to install a cordova module that could only be installed by yarn ( why? I have no idea, but trying to install it by npm did indeed fail )

after that everytime I had to build/prepare or other, I got an error…

I happened to make this error go away by passing totally to yarn…

After switching to another PC I now have again problem building/preparing…

And I cannot reproduce the setup that made it work…

Are other people here using yarn ? how do you make it work ?