Relationship has been changed automatically!!!

Dear Planner
I’ve faced very strange thing!!!, and I hope anyone knows its reason and gives its solution to solve that.
Imagine a project with following activity:


Activity………Successor………Predecessor
a…………………………………bFS………………………………
b…………………………………aFS………………………………
c…………………………………………………………………………


Activity………Successor………Predecessor
a…………………………………………………………………………
b…………………………………………………………………cFS
c…………………………………bFS…………………………………

When I close mentioned project and open it again (even when I close P3e and open it again) activity relationships have been changed!!!


Activity………Successor………Predecessor
a…………………………………aFS…………………………………
b…………………………………………………………cFS , aFS
c…………………………………cFS…………………………………

To solve mentioned problem even I used "purge deletes" but they couldn’t help me to solve that.

My program situation is:
1) Primavera 5, SQL
2) I’ve marked "Purge deletes when existing project management" in "admin preference"
3) Added "UseSPToPasteProject=0" to "pm.ini" to solve "loosing UDF data"

Thanks in advance
Amir Dadbakhsh