how to process returns 'buy' part as a 'make'

we have a part under serial control. our company was purchased. parts we used to make serial controlled, we now changed to  buy. items are being returned to replace a lower level bom part. as a buy item, we cannot create a discreet job and enter under routing tab where to 'start serialization'.

is the only solution to switch attribute back to 'make' to process returns.

on the other side the parts we now 'buy', we don't have the ability to enter lower level serial numbers (that may need to be replaced)

the issue is we buy parts but we also service them