Bingo ! That was it ! Put the render Pass to "Before Rendering Post Processing" and voilà :)
You're right for the infinite loops on Fancy Neon, Fancy Outline, Sobel Neon and Sobel Outline. Also may I report that when this happens, kill Unity, reopen it and just select the asset SnapshotRenderer and the infinite loop comes again. My work around is to delete the whole package from the local folder of the project and re-import the package.
Many thanks for your help and I hope you'll manage to muddle through the version issues :) See you soon!