In some cases the PDF file itself contains embedded data the printer cannot interpret so you get a 49 error.
firmware updates often include some fixes for 49 errors so if you upgrade the firmware as the first step, check driver is updated as well.
Another test is to ftp to the printer IP using the browser, drag and drop the file, see if it prints, if you get an error this has bypassed the print driver, the image would be single sided but it might help if you see the error or not.
With duplex the 2nd page is rendered first and rotated 180 degrees, the first page is rendered then printed, it might be a memory issue, one step you can do is to look in the print driver and you should be able to locate the DPI setting, drop it down to 300 dpi if its at 600, this will reduce memory requirements by 75%, if the image prints then it's a memory issue, if the error persists then likely to be embedded codes.
finally I would try using the Postscript driver (PS), as this will render the file differently to PCL and in some cases will work around these errors.