Using several variables in a complex measure returning incorrect result

Hi

I'd be grateful for some help. I've created a complex measure to add a regression line to a  line and clustered column chart. If I create all of the variables as separate measures, the line works perfectly.  However, it would be preferable to create as variables. When I use the measure below, I get different, incorrect results. Can anyone advise? Thank you 🙂 

Linear HW =
VAR Count_Items =
CALCULATE( COUNTROWS ( 'SALES' ), ALL( 'SALES') ,'SALES'[Town]="HW")

Var SumRank = SUM('SALES'[Dense Rank])

VAR Sum_X =
CALCULATE(SumRank,
FILTER(
ALL('SALES' ),
'SALES' [Town]="HW"
)
)

Var RankSqd = sumx('SALES','SALES'[Dense Rank]^2)

VAR Sum_X2 =
CALCULATE((RankSqd),
FILTER(
ALL('SALES' ),
'SALES' [Town]="HW"
)
)

Var SumValues = sum( 'SALES'[Rate per 100,000])

VAR Sum_Y =
CALCULATE(SumValues,
FILTER(
ALL('SALES' ),
'SALES' [Town]="HW"
)
)

Var YearSort_Value = Sumx('SALES','SALES'[Dense Rank]* 'SALES'[Rate per 100,000])

VAR Sum_XY =
CALCULATE(YearSort_Value,
FILTER(
ALL('SALES' ),
'SALES' [Town]="HW"
)
)

VAR Average_X =
Calculate(AVERAGEX('SALES','SALES'[Dense Rank]),
FILTER(
ALL('SALES'),
'SALES'[Town]="HW"
)
)

VAR Average_Y =
Calculate(AVERAGEX('SALES','SALES'[Rate per 100,000]),
FILTER(
ALL('SALES'),
'SALES'[Town]="HW"
)
)

VAR Slope =
calculate(
DIVIDE (
Count_Items * Sum_XY - Sum_X * Sum_Y,
Count_Items * Sum_X2 - Sum_X ^ 2),
FILTER(
ALL('SALES'),
'SALES'[Town]="HW"
)
)

VAR Intercept =
CALCULATE( Average_Y - Slope * Average_X,
FILTER(
ALL('SALES'),
'SALES'[Town]="HW"
)
)

RETURN

Intercept + MAX('SALES'[Dense Rank])*Slope