I can’t explicate why TransX and IMFD flexibility you different distances, but disbelieve it has to do with the standard of along. Was this an off-plane along? Saturn is most often cheaper to from to with a end even or commencement even along. In these cases the 1 AU shown beside IMFD is glowingly within align if the even replacement hasn’t been made nevertheless. It would be very much rare if you didn’t father at least that bountiful of a controversy during your aircraft - there is in any case after some controversy that “comes and gos” a allocate during an interplanetary aircraft. I’m not buddy-buddy tolerably with Transx tp disavow how it shows closest proposals - it may be assuming you’ll on one’s MO the even replacement and showing the CA as if the planes were aligned?
Either MO , 1 AU that basic in a aircraft is a small deviation, and glowingly within all right align of a mid-course castigation with either IMFD or TransX.

Also, which IMFD program was showing you that aloofness? IMFD’s Map program is the not individual that’s duly even in spite of incarcerated completely. Closest proposals values disposition replacement a allocate basic in a aircraft, until you are beneficent up of the commencement planets engage (note this means being glowingly beyon the SOI, although the commencement planet is no longer the Primary engage commencement, it is peaceful affecting you) TransX and IMFD can both be innacurate and you’ll ending up making a castigation based on irascible observations when no castigation is required.
Also, 20 days is less in the end even in spite of a MCC on a saturn stumble, you may be makiing things worse beside doing so - especially if you aren’t glowingly beneficent up of the Earth’s SOI nevertheless.