Documents with individual permissions reinheriting permissions after check in

Question

I have a folder within a SharePoint 2010 document library, with several excel spreadsheets within it.  The excel spreadsheets all have individual permissions on them.  Check-out is inforced on the library.  A user then checks-out their
spreadsheet, amends it and checks it back in.  The spreadsheet then loses it individual permissions and reinherits the permissions from the folder above.  Does anyone know how to prevent this from happening?  As we need to keep the individual
permissions.

Answer 1

looks strange. let us know some more details.
1. check the workflow if any associated
2. Check the is that document library created based on custom template
3. Upload a document to the library and break the permission. now check-out--> do some modification to the document--> save it-> check-in the document. Now check whether the permission remains or reinherited from parent
4. check if ant event receiver associated with content type if custom content type used.
Hope this will help you
Senthilrajan Kaliyaperumal