I have an old HP laserjet printer that has been connected to our desktop via parallel connection. It's worked for years around the WiFi house, but we had to keep the desktop turned on to print.
A while ago I acquired the small Netgear PS101 parallel print server that just plugs right into the Centronics port on the printer, and has an Ethernet jack to plug into your local wired LAN.
I don't know what might be happening ????? Maybe the ARP cache in the switch is getting flushed, or the server is going idle - but still broadcasts it's LPR existence.
Any thoughts ????