Component Allocation in Routing is missing

Dear PP Gurus,

We are using R/3 4.7 version and we are facing a serious problem in Routing Comp. Alloc. since few years. There are 3 to 5 operations in the Routing and about 20 to 30 BOM components, each components are assigned to their respective operations. But after a few days, component allocations for some materials would be gone. So the user needs to do the assignment again from time to time.

They don't even changed the BOM and there's only 1 person who is maintaining the Routing. So we don't assume that somebody has removed the component allocation. Besides, we have activated the Change Management in Routing since then, and we are able to see the history changes in the Routing.

If this is a System Bug, do you know any patches or OSS note that could fix the problem?

Thanks,

John