Well, I tried to write in French, but actually I found that some photo terms are unknown to me in this language... I can understand the parallax error possible with TLRs (cut-off foreheads, that's usually the trouble). Are your negatives sharp, after all? Different scale in a finder and on the negative should mean different focal lengths of the twin lenses, and it can't be done simple! And of course different length lenses in TLR setup won't give sharp pictures together. So the problem seems to be quite strange...