It seems to me I read in the past a recollection by Ansel Adams about the job of finding and fixing holes in the bellows but unfortunately I cannot find the source (was it "The Camera" book? Or maybe "Examples: The Making Of 40 Photographs"?).
From what I understood, a little hole in the bellows acts as an accidental pinhole camera and gives a very weak image which is anyway disturbing the main image.
I guess it was (it is still now?) a very common problem with the folding camera and so maybe it was described by many others photographers apart from Ansel Adams.
Is there anyone who can provide me a source/reference?