VBA 255 Maximum Characters in 1 Cell - excel

Question

I have a simple macro which adds the contents of each row in an excel sheet to a text file, with delimiters in between each cell value. This is done by running a for loop which iterates through each row and at the end of each iteration the values are added to the end of a String variable.
Each ROW can have a lot of characters in it - I have not noticed any issues with that. However, when 1 single cell contains more than 255 characters, the concatenation fails. I am not sure if it is because of String limitations (I don't think that is the case), or if it is the Trim, Join, or Index functions that contains this limitation, or if it something else. Any help in getting some more insight would be appreciated.
The line in question ('R' refers to the row/iteration number):
stringVariable = stringVariable & vbNewLine & Application.Trim(Join(Application.Index(Cells(R, "A").Resize(, 25).Value, 1, 0), "|"))
The error is:
Run-time error '13': Type mismatch

Answer 1

The problem is with the Application.Index. How to debug?
Let's have the active sheet with any values in row 1, all with less than 255 chars. But in one of this cells in row 1, for example in C1, should be the formula:
=REPT("c",255)
Now split the code into parts:
Sub test()
r = 1
v2DArray = Cells(r, "A").Resize(, 25).Value
index1DArray = Application.Index(v2DArray, 1, 0)
joinString = Join(index1DArray, "|")
stringVariable = Application.Trim(joinString)
MsgBox stringVariable
End Sub
This will work until you change the formula to =REPT("c",256). Now it will fail at Application.Index.
Instead of the Application.Index you could do the following:
Sub test2()
r = 1
v2DArray = Cells(r, "A").Resize(, 25).Value
ReDim v1DArray(LBound(v2DArray, 2) To UBound(v2DArray, 2)) As String
For i = LBound(v2DArray, 2) To UBound(v2DArray, 2)
v1DArray(i) = v2DArray(1, i)
Next
joinString = Join(v1DArray, "|")
stringVariable = Application.Trim(joinString)
MsgBox stringVariable
End Sub

Answer 2

After experimenting using different combinations of the already present functions, I found that the macro finishes without issues when Index is not used.
In the end I decided to add the value of each cell to the end of the string, one at a time. Solution:
For i = 1 To numberOfColumns
If i < numberOfColumns Then
stringVariable = stringVariable & Trim(Cells(R, i).Value) & "|"
Else
stringVariable = stringVariable & Trim(Cells(R, i).Value)
End If
Next i
stringVariable = stringVariable & vbNewLine