Generate Delta table to calculate deltas between two temp measurments

[#1]

I have a data table that combines 2 datasets for 2 temperature for multiple units. Each unit is subjected to 20+ tests at 2 temps.

I need to generate a delta table for each unit, that calculate the delta between temp2 - temp1 as shown in table "Data_Table".

I keep getting the same error after an incomplete delta table is generated shown next

the error I get 

My data table 

here is my code, if any can help I would really appreciate it

Names Default To Here( 1 );

dt = Current Data Table();

allCols = dt << Get Column Names( string );

tpColName = allCols[1];  // Always Column 1

dutColName = allCols[2]; // Always Column 2

testCols = {};

For( i = 3, i <= N Items( allCols ), i++, Insert Into( testCols, allCols[i] ) );

// 2. Extract Unique Values

Summarize( dt, dutList = By( Column( dt, 2 ) ) );

Summarize( dt, tpList = By( Column( dt, 1 ) ) );

// 3. Setup Results Table

dt_delta = New Table( "DUT Delta Results" );

dt_delta << New Column( "DUT", Character, Nominal );

dt_delta << New Column( "Shift", Character, Nominal );

For( i = 1, i <= N Items( testCols ), i++,

dt_delta << New Column( testCols[i] || " Δ", Numeric, Continuous )

);

// 4. Robust Calculation Loop

For( d = 1, d <= N Items( dutList ), d++,

currDUT = dutList[d];

For( t = 2, t <= N Items( tpList ), t++,

p1 = tpList[t-1];

p2 = tpList[t];

// This forces a match even if your DUT/TestPoints are numbers

r1Mat = dt << Get Rows Where( Char( Column( dt, 2 )[] ) == Char( currDUT ) & Char( Column( dt, 1 )[] ) == Char( p1 ) );

r2Mat = dt << Get Rows Where( Char( Column( dt, 2 )[] ) == Char( currDUT ) & Char( Column( dt, 1 )[] ) == Char( p2 ) );

// Ensure exactly one row found for each point to prevent subscript errors

If( N Rows( r1Mat ) > 0 & N Rows( r2Mat ) > 0,

row1 = r1Mat[1]; // Explicitly take first found row as integer

row2 = r2Mat[1];

newRow = dt_delta << Add Rows( 1 );

dt_delta:DUT[newRow] = currDUT;

dt_delta:Shift[newRow] = p2 || " - " || p1;

For( c = 1, c <= N Items( testCols ), c++,

colN = testCols[c];

v1 = Column( dt, colN )[row1];

v2 = Column( dt, colN )[row2];

If( !Is Missing( v1 ) & !Is Missing( v2 ),

Column( dt_delta, colN || " Δ" )[newRow] = v2 - v1

);

);

);

);

);

dt_delta << Bring Window To Front;