Hi Loke, I'm not sure I get it, but let's see, Is your form a header-detail (parent child), type of form, like an invoice?. Are the child records the ones who get crossed?. If this is the case it would be very hard to guess what's going on without knowing the actual code that is used to assign the foreing key values. At a first glance I would think that you're assuming the last record in the parent table is the one you should take the foreign key number from, a little unorthodox but could be causing the problem, but then again it doesn't seem to be the case. If I understood your problem it's something like this

Header:

pk 111

Detail:

record 1 = fk 111, value A
record 1 = fk 111, value B
record 1 = fk 111, value Z ???? But the user typed C, this is form the other user

For the other user:

pk 222

Detail:

record 1 = fk 222, value X
record 1 = fk 222, value Y
record 1 = fk 222, value Z

I'd say step through the process and check for the moment you loose the valu