I am having the same issue on a C605 running the latest software (v. 62.66.11). Setting the bypass tray to Letter/Letterhead/White and sending a print job from MS Word 365, the device duplexes the Letterhead and prints on the back of the page. I tested using the latest PCL6 and PS GPD drivers. They both get the same results. I duplicated on multiple devices running different firmware versions.
There are similar issues posted from 2017 that references a firmware update that did not correct the issue.
Is this still an issue? Is there a fix?
Yes, that is how the media is being loaded to make the C605 print correctly. The issue is, the device is duplexing Letterhead even though the driver is set to 1-Sided print. This forces the user to load the paper different than the image on the Bypass tray and significantly slows the printing of Letterhead. I have duplicated this behaviour on multiple VersaLink devices and firmware versions.