Two xerox free flow access print queues stops sharing by its own and unchecked the shared printer option for these print queues. They used to have this problem and being happened more frequently now after the network change.
This is only happening for these Xerox Free flow drivers. The print server runs 2016 64 bit and xerox doesn't list out drivers of this OS level. The last driver release of these plotter type was server 2008 64 as per this URL : https://www.support.xerox.com/support/xerox-6204/downloads/enus.htmloperatingSystem=wins2008x64&file...
At present it has the driver version: Xerox FreeFlow Accxes Printer Drivers v15.0.5