Lookup not functioning as expected

Hi experts,

We are trying to use the lookup function to map the stocks of one class to another class.

BUWPRclsTfrTo measure is a drop-down (picklist) which selects the destination class

In order to use the lookup, the index of the above is then fed into the lookup function as given below.

BUWPRclsTfrOut = index([prod].[clss],BUWPRclsTfrTo).

BUWPRclsTfrOut is used to get the index.

BUWPRclsTfrInR <- lookup(BUWPRclsTfrOutR,[prod].[clss],BUWPRclsTfrOut )

BUWPRclsTfrOutR is editable stock measure of the source class.

All measures BUWPRclsTfrOutR, BUWPRclsTfrInR,  BUWPRclsTfrTo,  and BUWPRclsTfrOut are at week (clnd)/country(locn)/class(product)/stock-type intersection.

BUWPRclsTfrOut is my mapping measure.