After linking, it come out #REF!

[DavidPonnet]

After ive have been linking over 100 cells between 2 different excel files, all of a sudden, my links all went #REF! and I have to start over

=VLOOKUP(D459;'[1. Speedo Cases GEM 170728.xlsx]speedo'!$B$10:$FZ$115;3;FALSE)

became

=VLOOKUP(D483;#REF!;3;FALSE)

Any one has an idea how this happened or how I can prevent it from happening ? I´m really not happy about this as its multiple hours of work ive lost ...

 

[DavidPonnet]

I have found that, when i open the file with the links first, and I open the file where the links are linked to after, all my formulas end up as #REF !

Could any one have an idea whats going on ? Never had this before