eps images dissappear after updating the eps

[frame user]

Hi,

If I have a framemaker file with linked eps images and I open the eps images
and resave them in a more recent version that the original eps file (i use
for example illustrator CS to open the file but they can be made in a
previous version of illustrator) then some images just dissappear in the
framemaker file.
They are just gone, I need to import them again.
The strange thing is that this occures with some images but not all.
Does anyone have an explanation/solution for this?

Thanks!