Is really Traktor erasing links to stems when upgrading ?

Hi

I have recently upgraded Traktor 4 from 4.0.2 to 4.1

And didn't realize immediately that all my stems (that took me days of converting one by one) are not anymore reconized …

Actually the stems folder it still there, but the stems icons disappeared from all files I have already converted

I just can't believe the upgrade deleted many days of work and that NI didn't have a solution for this …

Is anyone know a solution to relocate everything ?

Thanks you in advance