VBA-PCOMM Macro runs in F8 but not in F5

Question

I've been working on PCOMM-VBA macros for a couple of months now. This issue is mostly happens with every macros I write. Although not every cases when I try to run the macro.

I am quite suspicious that the source of the problem is PCOMM cannot keep up with excel hence some parts of the code will be skipped. However reading a couple of posts make me feel maybe excel have some problems with the loops and activesheet in my code. I am not sure what causes the issue but I hope you can direct me to the answer.

The macro's purpose is to update suppliers' email address. To select the suppliers I've created a template which contains the supplier code and couple additional information along with the email address needs to be uploaded.(4 column with a simple .xls)

So be brief: When I run the code in F8 the code runs through without any errors. When I try to run it in F5 the compiler will skip some lines and make an infinite loop (as the requested data will never appear in the field) or worse case actually update it with the wrong data.

Here is the actual code:

Sub email_upload()

Dim appExcel As Excel.Application
Dim appWb As Excel.Workbook
Dim appWs As Excel.Worksheet

'This part creates a connection between an existing PCOMM session and Excel
Set autECLConnMgrObj = CreateObject("PCOMM.autECLConnMgr")
Set autECLOIAObj = CreateObject("PCOMM.autECLOIA")
Set autECLSessionObj = CreateObject("PCOMM.autECLSession")
Set autECLPSObj = CreateObject("PCOMM.autECLPS")
Set autECLConnList = CreateObject("PCOMM.autECLConnList")

autECLOIAObj.SetConnectionByHandle (autECLConnList(1).Handle)
autECLPSObj.SetConnectionByHandle (autECLConnList(1).Handle)
autECLConnList.Refresh

'Opens the template where the supplier codes are in (normal .xls)
With Application.FileDialog(1)
    .Title = "Please select a file to import!"
    .AllowMultiSelect = False
    If .Show <> -1 Then
        Exit Sub
    End If
    FileSelected = .SelectedItems(1)
End With

fileName = FileSelected

Set appExcel = Excel.Application
Set appWb = appExcel.Workbooks.Open(fileName:=fileName)
Set appWs = appWb.Worksheets("input")

appExcel.Visible = True
appWb.Worksheets("input").Activate

With appWs

autECLOIAObj.WaitForAppAvailable

'Loop thru every row in the template worksheet 
For i = 2 To Cells(Rows.Count, "A").End(xlUp).Row Step 1

'Start system navigation in AS/400
autECLPSObj.SetCursorPos 6, 23
autECLPSObj.SendKeys Cells(i, "A")
autECLPSObj.WaitForAttrib 6, 23, "00", "3c", 3, 10000
autECLOIAObj.WaitForInputReady
autECLOIAObj.WaitForAppAvailable
autECLPSObj.SendKeys "[enter]"
autECLOIAObj.WaitForInputReady
autECLOIAObj.WaitForAppAvailable
autECLPSObj.SendKeys "[pf13]"
autECLOIAObj.WaitForInputReady
autECLOIAObj.WaitForAppAvailable
autECLPSObj.SendKeys "[pf10]"
autECLOIAObj.WaitForInputReady
autECLOIAObj.WaitForAppAvailable
autECLPSObj.SetCursorPos 13, 24
autECLPSObj.SendKeys Cells(i, "B")
autECLPSObj.WaitForAttrib 13, 24, "00", "3c", 3, 10000
autECLOIAObj.WaitForInputReady
autECLOIAObj.WaitForAppAvailable
autECLPSObj.SendKeys "[enter]"
autECLOIAObj.WaitForInputReady
autECLOIAObj.WaitForAppAvailable
autECLPSObj.SendKeys "[pf8]"
autECLOIAObj.WaitForInputReady
autECLOIAObj.WaitForAppAvailable

If Cells(i, "C") = "" Then
    autECLPSObj.SetCursorPos 13, 21
    autECLPSObj.SendKeys "1"
    autECLPSObj.WaitForAttrib 13, 21, "00", "3c", 3, 10000
    autECLOIAObj.WaitForInputReady
    autECLOIAObj.WaitForAppAvailable

Else
    autECLPSObj.SetCursorPos 13, 21
    autECLPSObj.SendKeys Cells(i, "C")
    autECLPSObj.WaitForAttrib 13, 21, "00", "3c", 3, 10000
    autECLOIAObj.WaitForInputReady
    autECLOIAObj.WaitForAppAvailable
End If

autECLPSObj.SetCursorPos 21, 1
autECLPSObj.SendKeys Cells(i, "D")
autECLPSObj.WaitForAttrib 21, 1, "00", "3c", 3, 10000
autECLOIAObj.WaitForInputReady
autECLOIAObj.WaitForAppAvailable
autECLPSObj.SendKeys "[pf8]"
autECLOIAObj.WaitForInputReady
autECLOIAObj.WaitForAppAvailable
autECLPSObj.SendKeys "[pf12]"
autECLOIAObj.WaitForInputReady
autECLOIAObj.WaitForAppAvailable
autECLPSObj.SendKeys "[pf12]"
autECLOIAObj.WaitForInputReady
autECLOIAObj.WaitForAppAvailable

Next i

End With

appWb.Close
MsgBox ("Input done!")


End Sub