A Query on FRx

To all FRx Consultants available, kindly read the below query from one of my colleagues and please send in your inputs as comments to this post. Any help is highly appreciated:

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In a row format, I have a calculated row which joins the values from 6 non printing row to it like below.

220 NP
250 NP
280 NP
310 NP
340 NP
370 NP
400 CAL A = A220, B TO X = B220 TO X220, Y TO AR = Y250 TO
AR250, AS TO BK = AS280 TO BK280, BL TO CE = BL310 TO CE310, CF TO CY = CF340
TO CY340, CZ TO DP = CZ370 TO DP370.

If i print the report seperately using this row format, it prints fine.

But when i add that row format(as a reporting unit) to an existing report
tree, while printing it shows the "Error in calculated formula in [400]".

Any idea of why its happening only in reporting tree?
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VAIDY