Error when trying to perform RAW print

[mwatz122]

Whenever I try to perform a RAW print (send byte stream directly to printer), I receive the following error message on the printer display:

Print data has been received that may not be complete. To print the existing data, press OK. To exit help and wait for the command to print the last page, press ?.

I am attempting to print a PDF that is only 69.3 KB in size. Also, not only am I having this problem with PDF's, but the issue occurs when trying to RAW print anything at all (even a simple string of "Hello, world!" text).

As for how I'm accomplishing this, I am performing a RAW print programmatically using the winspool.dll / Windows API very similar to the example seen here https://support.microsoft.com/en-us/help/322091/how-to-send-raw-data-to-a-printer-by-using-visual-c-.... The file bytes are sent to the API and print correctly on several other  HP printers I have tested on, but I always get the "Data received" error shown above on my HP LaserJet M604 printer. After pressing OK, the PDF prints normally (but of course this is annoying).

The file is a valid PDF which is terminated with %%EOF. If I open the PDF in Adobe Reader and try to print, everything works fine. I am specifically encountering this problem when performing a RAW print sending the bytes as a stream. I am using the latest firmware and have tried reinstalling the printer and changing a plethora of settings. Of course, I have also tried multiple drivers, but I believe the drivers are being bypassed in this situation anyway.

If it helps, I am using Windows 7 Professional (32-bit). I would greatly appreciate any insight that may lead to finding a solution for this issue! Thank you.