Few Sales orders Object link is disappeared in cProjects

Hi All,

I am getting issue in eProject .When I open a project in eProject object link is disappeared for few sales orders I am not able to see the object link.

To see missing object links in project now I am creating manually then I able to see the  object link.

Any one have idea why few project not showing object link sales order.

Please see the screen shot.

Object links is missed below screen shot.

I checked in below link 'own persistence' not checked.

Created Object link is disappeared

Thanks,

Preddy.