SendKey does not send full String in VBA (using IE)

I'm currently trying to select a file to upload automatically on a website using VBA. I am stuck at the file choice, when the file browser windows pops up. Using SendKeys I try to send the full path the the file I'm trying to upload (filepath1, it is pretty long), but the SendKeys function only ever returns half of the string path or so, and doesn't respect the enter commands. The SendKeys function also works one time of out two.. leaving the search bar empty from time to time. I've seen a lot of people complaining about this on the net but no other solution then to pause the application between calls, which is what I did. I've used Public Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long) in a module to define the Sleep 1 calls. Can anyone help me out here? Any help will be much appreciated thank you!

Sub GenerateKML_Macro()

' GenerateKML Macro
Dim IE As New InternetExplorer
Dim ExplorerInput As HTMLInputElement
Dim ExplorerButton As Object
Dim IEDoc As HTMLDocument
Dim NextThingy As Object
Dim iBox As HTMLIFrame
Dim iframeDoc As HTMLDocument
Dim filepath1 As Variant
Dim name_of_file As Variant

    filepath1 = "...\Excel_Template\Template.xlsx"
    name_of_file = "Template.xlsx"
    'Load
    IE.navigate "https://www.earthpoint.us/ExcelToKml.aspx"
    'Show
    IE.Visible = True
    'Wait
    WaitIE IE
    'Select document
    Set IEDoc = IE.document

    WaitIE IE

    Set iBox = IEDoc.all("iframe1")
    Set iframeDoc = iBox.contentDocument
    Set ExplorerButton = iframeDoc.all.Item("FileUpload1")
    'ExplorerButton.Click
    Sleep 1
    ExplorerButton.Focus 'can't set ExplorerButton.value directly for security reasons
    Sleep 1
    Application.Wait Now
    Sleep 1
    SendKeys (filepath1)
    Sleep 1
    SendKeys ("{ENTER}")
    Sleep 1
    SendKeys (name_of_file)
    Sleep 1
    SendKeys ("{ENTER}")
    Sleep 1
    'Wait
    WaitIE IE

    'Close
    'IE.Quit

    'Unload
    Set IE = Nothing

End Sub

Sub WaitIE(IE As InternetExplorer) 'Loop until page is loaded Do Until IE.readyState = READYSTATE_COMPLETE DoEvents Loop End Sub

Ps: However many times I ran the application the SendKeys never managed to select the Template.xlsx file I'm trying to reach. I devided the search path in two variable to make it clearer, but nothing came out of it.