Hi,
You have semi finished product and posting MIGO with movement type 101 but posting MIGO with respect to purchase order or production order?
Also check semi finished product price in material master record with price control which cause your concern.
Also check valuation class for semi finished product in MM03 and find G/L account assignment with BSX key with valuation class of semi finished product in t.code:OBYC with chart of account.
Also cross check your plant 4001 assigned to valution grouping code in t.code:OMWD
Regards,
Biju K