When the ChunkSize of RadAsyncUpload is set the files are not fully uploaded. A sample excel file to reproduce the issue is attached to this reply.

Remove the ChunkSize setting of the AsyncUploade:

        <telerik:RadAsyncUpload ID="UploadFile" runat="server" MultipleFileSelection="Automatic"
            OverwriteExistingFiles="true" ReadOnlyFileInputs="true" InputSize="45" EnableViewState="true" TargetFolder="~/UploadedFiles">
        </telerik:RadAsyncUpload>

Steps to reproduce:

1. Run the following configuration and upload the attached to this item file
        <telerik:RadAsyncUpload ID="UploadFile" ClientIDMode="AutoID" runat="server" MultipleFileSelection="Automatic"
            OverwriteExistingFiles="true" ReadOnlyFileInputs="true" ChunkSize="3145728" InputSize="45" EnableViewState="true" TargetFolder="~/UploadedFiles">
        </telerik:RadAsyncUpload>
        <telerik:RadButton runat="server" Text="Upload"></telerik:RadButton>


Expected: An 11MB file is uploaded
Actual: An 8MB file is uploaded (the last chunk part is missing)