Im doing a testing for my new Odoo9 setup

I did a purchase order for
i) Item1 - 100units - $5.00each
ii) Item2 - 50dozens - $12.00each ($1.00perUnit)
Total Cost $1100.00

I received Item2 in two lots (300units/300units).

I did a Landed cost of $77 (7%) tax, split by costing ($35/$42) was accurate and so is stock valuation.

I did a sales order + invoice + delivery
a) Item1 - 100units @ $10each , Item2 - 300units (150units from Lot1, 150units from Lot2). @ $2.25 each.

The problem is the accounted value (COS) for item1 is correct at $535.00
But the accounted value for 150units Lot1 is $276.00 , and 150units Lot2 is $276.00
This would amount to cost of $1.84 for each (which should be $1.07)

Now when i sold the balance stock of (150units/150units) the accounted value COS is still $276/$276.
Now my Inventory account is at -$462.00 , and my Inventory Valuation is zero.

Is this a bug? This would be disastrous when i commit to Odoo for my stock inventory and accounts.