Alan, the Sync option for manually changed records is set to "do not update"
for the moment, I spend my free time to alter my DB to "N" for auto update, ad a timestamp and a filename in PTTN, and also delete the regular LK/LK1 and PT/PT2 fields for the records I have a recent/correct picture.
this work will take me several more weeks, meanwhile, I simply don't have the time to check if updates alter my work back to scratch (for the moment I do not connect my box anymore, just launch the program to work with the DB explorer ).
maybe if I get to the "OO-" part of the DB, i'll be able to spend a couple of days checking out some settings, but this lies WEEKS ahead of me.
meanwhile, thanks for the tips and suggests so far ( and I second Netcops suggestion for the "Do not overwrite existing aircrafts records" option )