Ability to change the Line manager in past records

Hello Team,

while we are trying to add BPFM details for past employee assignment records, BPFM data is replicating future records too.

It occurred in Production.

In addition to this scenario when we try to create manager records to the terminated employees in the past.

The created manager details are visible in system on terminated record which is odd. Currently manager details won't be available on terminated records. 

Could you please help us to resolve the issue as much as possible. Experts any suggestions please.

Thanks,

Paramesh