The Problem with print spooler service when join L300 to server

My systems are using Ncomputing L300 device to connect to server is running windows server 2012 R2 there are using Vspace Pro 10.3 to management Ncoms client. At each Ncomputing client have a laser printer or dot-matrix printer connected to them. But sometime there are some printers disconnected (check in Printers and fax they are offline) and They have just online return when I restar Print spooler service or restart the server but sometime failure. The proplem happen eternally with our systems, Pls give me a solution to fix this error.

(Our system are running base on Vmware ESXi and we have for 8 servers are using Vspace for Ncomputings client, all them having same a problem as above)

Thanks for your support