query.Experssion.Error - not seeing the cause

I have this function which is producing the error
An error occurred in the ‘’ query. Expression.Error: The name 'BytesPerIncrement' wasn't recognized. Make sure it's spelled correctly.
I cannot tell why BytesPerIncrement is producing this error and RemainingBytes is not.

(firstRows as table, t as table, procCal as list) as table =>
let
  prevRows = Table.ToRecords(t),
  newRows = List.Transform(prevRows, (row) => Record.TransformFields( row, {
let
  posrow = List.PositionOf(prevRows, row),
  RemainingBytes = fnRemBytes(posrow, prevRows, firstRows),
  BytesPerIncrement = fnBytesInc2(posrow, prevRows, firstRows, procCal),
  ScheduleIncrements = if BytesPerIncrement > 0
    then prevRows{posrow}[Schedule Increments] - 1
    else
      if RemainingBytes = 0
      then 0
      else prevRows{posrow}[Schedule Increments],
  RemainingDuration = if BytesPerIncrement > 0
    then
      if prevRows{posrow}[Remaining Duration] - SchedulingInterval < #duration(0,0,0,0)
      then #duration(0,0,0,0)
      else prevRows{posrow}[Remaining Duration] - SchedulingInterval
    else
      if RemainingBytes = 0
      then 0
      else prevRows{posrow}[Remaining Duration]
in
  {"Remaining Bytes", each RemainingBytes},
  {"Bytes Per Increment", each BytesPerIncrement},
  {"Schedule Increments", each ScheduleIncrements},
  {"Remaining Duration", each RemainingDuration},
  {"EndDateTime", each null}
})
),
outRows = Table.FromRecords(newRows)
in
outRows