Fixed cell get overwritten when quantity is changed at aggregate level

Gurus,

We have SCM 5.1 service pack SAPKY51006.

Issue: When we change quantity at aggrgate level for partial fixed cell, the fixed value at detail level also get changed.

For example: 100 is partial fixed at aggregate level, it is diaggregated as 25, 50 (fixed), 25 at detail level, If we change 100 to 200, quantuty at details level changes to 67, 67 and 67. weI expect, as 50 is fixed, it shoud not get overwritten by 67.

When we try this in SCM 2007, it works as desired. I am not able to find OSS note. is anybody have a clue

Thanks

Sujit Singasane