Copying array into workbook which is part of a collection gives run time error 451 in VBA

as part of some VBA for Excel that I'm writing I would like to print a 12 x 101 element array (dwt_percentiles) that is part of an item in a collection to a workbook so that I can make some graphs from the data. I have only started using classes in VBA in the past 24 hours and have got stuck on the following issue:

The line in the function where I am attempting to print the array throws the following error: "Runtime error 451: Property let procedure not defined and property get procedure did not return an object". The dwt_percentiles array is showing up fine with expected values when I add colltasks to the watches window, but I can't seem to access it from the code. I can access the other properties of the items of the collection fine, so it's probably an error in how I'm trying to access the array, but I can't find any similar code to what I'm attempting online (probably because I use the wrong terminology...).

The code I'm using is as follows:

Function plotECDF

Sub plotECDF(ByVal colltasks As Collection)

    Dim item As Variant
    Dim i As Integer, j As Integer, k As Integer
    
    For i = 7 To 13
        Sheet3.Range("A1").Value = i
        Sheet3.Range("B1").Value = colltasks(i).Name
        
        For j = 1 To 12
            For k = 0 To 100
                ' error shown on next line - run time error 451
                Sheet3.Cells(1 + j, 3 + k).Value = colltasks(i).dwt_percentiles(j, k)
            Next k
        Next j
                
    Next
    
End Sub

Class module Task - tasks form the elements of a collection

Option Explicit

' Basic properties
Public Name As String
Public Hs As Double
Public Ws As Double
Public window As Double

' Array definitions
Public dwt_array As Variant
Public dwt_byMonth As Variant
Public dwt_percentiles As Variant

Code which creates dwt_percentiles() array and sticks it in a collection

Sub do_things()

Dim percentileByMonth() As Variant
Dim percentileSum As Double
Dim percentileArray() As Variant
Dim numYears as Integer, j as Integer, jj as Integer, k as Integer
Dim t as New Task
Dim colltasks as New Collection

percentileSum = 0
ReDim percentilesByMonth(1 To 12, 0 To 100)
For j = 1 To 12
   For jj = 0 To 100
      For k = 1 To numYears + 1
         percentileSum = percentileSum + percentileArray(j, k, jj)
      Next k
                
      percentilesByMonth(j, jj) = percentileSum / (numYears + 1)
      percentileSum = 0

    Next jj
Next j

t.dwt_percentiles = percentilesByMonth

End sub

Many thanks.