Excel VBA Run-time error '1004': "Application-defined or object-defined error" when assigning Range.Value Property

OK, I've seen a lot of similar questions on here, but in all the ones I found, either there wasn't an answer, or it wasn't the same as my situation and didn't apply, or I tried the solution and it didn't work for me.

Issue is, in my code snippet below, I am getting "Run-time error '1004': Application-defined or object-defined error assigning Range.Value Property"

I do have Option Explicit set.

R, NR, and RungTopRow are all declared as integer types earlier in the code. CommentRow is also an integer (only ever equal to 0 or 1, declared as an integer rather than Boolean because I use the 0 or 1 as a multiplier in equations). CurrentCell is declared as type Range. LadderSheet is of type Worksheet set to a specific worksheet in my Excel file. I have used LadderSheet numerous other times in my program without any issues. RowSize is a defined constant equal to 6. thatRung is a class variable of type Rung that I have defined. CommentText is a public variable that is declared as part of the Rung Class. I have tried declaring CommentText as a string and defining it as a variant. I get the same error either way. Option Explicit is also set in the Rung Class Module.

NR is the number of Rungs in a ladder logic source that I'm using. This is only part of my code, additionally I have code to exit the program if RungTopRow ever equals or exceeds the maximum number of rows allowed by excel by comparing to a defined Const LastXLRow = 1048576.

Regardless, when I insert a breakpoint, I find that I'm getting the error on a value of RungTopRow = 3. So, I'm definitely not exceeding the maximum row.

Everything I've bundled into {Other Code Here} can run without error when I comment the below section out. Actually everything runs otherwise as expected if I comment out the .value assignment statement.

    For R = 0 To NR
        
    If R = 0 And CommentRow Then
        With LadderSheet.Range("C" & CStr(RungTopRow + 1) & ":P" & CStr(RungTopRow + RowSize - 1))
            .MergeCells = True
            .ShrinkToFit = False
            .WrapText = True
        End With
         Set CurrentCell = LadderSheet.Cells(RungTopRow + 1, 3)
        'this line keeps giving an application defined error
        CurrentCell.Value = thatRung.CommentText

    End If

    ... {Other Code Here} ...

    Next R

First I tried

LadderSheet.Cells(RungTopRow + 1, 3).Value = thatRung.CommentText

I replaced LadderSheet.Cells(RungTopRow, 3) with CurrentCell as that worked for me in another similar situation, but for some reason isn't working here.

I have also tried

currentComment = thatRung.CommentText
currentCell.Value = currentComment

With currentComment and thatRung.CommentText declared as strings. I get the same error, triggering on the assignment statement of currentCell.Value , so it is not due to the definition of thatRung.CommentText

Note that if I directly assign it to a literal string as follows:

CurrentCell.Value = "hello"

or as follows:

currentComment = "hello"
currentCell.Value = currentComment

It executes without issue. Of course, I don't get the text I actually want in that case. I need the text stored in thatRung.CommentText to go into the cell defined by the range CurrentCell.

Update The Rung Class is too big to post here, but the only place where CommentText is mentioned is in the delcarations as follows:

Option Explicit
'These values are directly defined
Public Number As Integer
Public NumBranches As Integer
Public RungType As String
Public CommentText As String 'Neither string nor variant working
Public RungText As String

'These values will need to be calculated
Private Branches() As Branch
Private Items() As Item
Private ItemsEmpty As Boolean
Private CommandsEmpty As Boolean
Private InputsEmpty As Boolean
Private OutputsEmpty As Boolean
Private BranchesEmpty As Boolean

Const maxItemsperRow = 4 'Make sure other modules have same value in constant

Perhaps also relevant are places where CommentText is manipulated prior to the code I posted above in the following line in my main module code (ImportL5x):

thisRung.CommentText = thisRung.CommentText & ThatXMLTag.Contents

The code I posted is in a subroutine called DrawRung and thisRung is passed to DrawRung as an argument:

DrawRung thisRung

And DrawRung is defined with thatRung:

Public Sub DrawRung(thatRung As Rung)

ThatXMLTag is another custom class I defined called XMLTag. Contents is also a string.

This is all of the code for the XMLTag class (it is only declarations right now, everything is assigned externally in another module):

Option Explicit

Public Enum XMLType
   XMLStart = 0 'No starting /, no ! data
   XMLContent = 1 'Starting !
   XMLStop = 2 'Starting /
   XMLUnknown = 3 'Anything else
End Enum
Public Name As String
Public Contents As String
Public TagType As XMLType