The "effective client name" of a remote slave is currently:
p4Client

+ hostname

P4 will behave badly if there is more than one slave running on that remote host that can execute a given job.

Proposed fix is to insert the following line after 848 of PerforceSCM.java
p4Client += "-" + buildNode.getNodeName().hashCode();

This will guarantee a unique but repeatable client name for each slave running on a remote computer regardless of the number of slaves.