Problem with auto reservation in production order component

hollydonut

hi all,

i have encountered a strange scenario with auto reservation this is happen in production order component.
i have an item with reserve - always.
when i add component line from Released Production Order>Line>Component
then i click Function button >> reserve
the problem is system reserving from purchase line instead of item ledger entry, while there is sufficient qty in inventory.
can someone teach me why is this happening?
if possible i want to know which code that create the reservation.
i have try to debug, but i am lost in the middle

thanks all.