It's possible for Vendor ID, Product ID and USB serial number to recognize USB devices. 
But various printers with the same ID cause to hang up a PC.
To prevent from such troubles, each printer should be made to allot different USB serial numbers.
Note that different serial numbers let you find the demand from each printer driver in Windows.

The setting process is different among printers.

POS printers
The default USB interface serial number is set "00000000" in main POS printers. You can change the default number by POS printer utilities.
Download it form below web-site.
http://www.citizen-systems.co.jp/english/support/download/printer/utility/software/index.html

Barcode printers
The default USB serial number is set invalid in barcode printers.
It's no problem to connect among printers with the same ID, but the position of each USB port is essential.
Make a USB serial number effective and set another serial number in order to reconnect.
You need barcode printer utilities. Download it from below web-site.
http://www.citizen-systems.co.jp/english/support/download/printer/utility/software/index.html