The issue still exists, it's definitely a bug.
I used to download files without any problems until it started to throw errors from time to time. Files are .xlsx and preview works perfectly.
{ "errorCode": "2200", "message": "ErrorCode=ExcelUnsupportedFormat,'Type=Microsoft.DataTransfer.Common.Shared.HybridDeliveryException,Message=Only '.xls' and '.xlsx' format is supported in reading excel file while error is ' at ICSharpCode.SharpZipLib.Zip.Compression.Streams.InflaterInputBuffer.ReadLeByte()\r\n at ICSharpCode.SharpZipLib.Zip.Compression.Streams.InflaterInputBuffer.ReadLeInt()\r\n at ICSharpCode.SharpZipLib.Zip.ZipInputStream.GetNextEntry()\r\n at NPOI.OpenXml4Net.Util.ZipInputStreamZipEntrySource..ctor(ZipInputStream inp)\r\n at NPOI.OpenXml4Net.OPC.ZipPackage..ctor(Stream filestream, PackageAccess access)\r\n at NPOI.OpenXml4Net.OPC.OPCPackage.Open(Stream in1)\r\n at NPOI.Util.PackageHelper.Open(Stream is1)\r\n at NPOI.XSSF.UserModel.XSSFWorkbook..ctor(Stream is1)\r\n at Microsoft.DataTransfer.ClientLibrary.ExcelUtility.GetExcelWorkbook(String fileExtension, TransferStream stream)'.,Source=Microsoft.DataTransfer.ClientLibrary,''Type=ICSharpCode.SharpZipLib.Zip.ZipException,Message=EOF in header,Source=ICSharpCode.SharpZipLib,'", "failureType": "UserError", "target": "Copy data", "details": [] }