Years ago I found it much easier to switch over those 6400 line printers to remote output queues.
Here’s another link for troubleshooting timeout issues with AS400 printers. To start you need to compare the device configurations with the two printers reporting the error with the one that’s not. (Also check cabling and power conditions in this work area, maybe there’s something happening here that’s not a simple device time-out issue)
Finally what I’ve done for 2nd and 3rd shift operations when there’s no IT support is to set up a Job Scheduler entry to run every 1-4 hours depending on the environment to run the <b>STRPRTWTR *ALL</b> and <b>STRRMTWTR *ALL</b> commands. This isn’t a great solution but it beats the heck out of getting a 2 am phone call when your sleeping about a critical document not printing out somewhere in your company.