Console output:

Started by timer
Building remotely on........ (linux RHEL6) in workspace <...........>
P4: Unable to connect: com.perforce.p4java.exception.ConnectionException: The authenticity of '.............:1999' can't be established,
this may be your first attempt to connect to this Perforce server.
The fingerprint for the public key sent to your client is
DF:7A:EF:AA:77:E2:D6:45:89:A4:5F:6C:44:93:7D:CC:33:75:92:ED
To allow connection use the 'addTrust' method with the 'autoAccept' option.
P4: Connection retry: 1
P4: Connection retry giving up...
P4: Unable to setup workspace: java.lang.NullPointerException
P4: Unable to close Perforce connection.
ERROR: P4: Unable to setup workspace: java.lang.NullPointerException

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This issue is happening sometimes, this jobs is triggered every 5 minutes. Even we check that other build is finished successfully in this same slave.