Named Lambda Function doesn't work inside another

[JackDanIce]

Hi,

I have this LAMBDA function "Flag_Sum" which works fine at spreadsheet level:

=LAMBDA(calc, flag, lag, LET(
    flaglag, flag + lag,
    padding, SEQUENCE(flaglag, , 0, 0),
    sum_calc, DROP(MAP(calc, LAMBDA(flaglag, SUM(OFFSET(flaglag, , , flag)))), -flaglag),
    VSTACK(padding, sum_calc)
))

I am trying to call it function "Full_Build":

=LAMBDA(date, prices, captive, custom, lag, flag1, LET(
    price_change, Price_Change(prices),
    s, captive - custom,
    a, Flag_Sum(s, flag1, lag),
    k, HSTACK(date, price_change, s, a),
    k
))

As far as I can break down, SUM(OFFSET(flaglag, , , flag)) in "Flag_Sum" is giving an output that isn't an array to fit step "a" in "Full_Build", but called alone, "Flag_Sum" correctly spills at spreadsheet level.

Can anyone else what the issue is?

TIA,
Jack