Multi IFS Print Agents - Problem

We have 2 MWS on the same server, (IT2 and IT3) and 2 print agents installed 1 for IT2 and 1 for IT3. 

The print agent was installed for IT2 and this works without any issues.  However, when we start the print agent for IT3 the IT2 print agent ceases to work and stops.  On stopping the IT3 print agent and starting the IT2 print agent again it works without any problems.

The print agents have been installed on the same application server where IT2 and IT3 MWS reside.

Any tips/advice?

Thank you.