Cash Flow Value Issue

@ISMBR("Jan")

For 'Cash and Cash  Equivalents, Beginning of Period' account, the Time Balance is set to 'First' and the Member Formula is as follows:

IF ( @ISMBR("Jan") ) 

@MDSHIFT("Cash And Cash Equivalents"->"Dec",-1,Years,);

ELSE

@PRIOR("Cash And Cash Equivalents");

ENDIF

In the FR report, everything is working, including Q-T-D (month), except for Y-T-D (month), where Y-T-D (month) produces a zero value.

Has anyone seen this issue before and can shed some light on the issue?

Thanks!