There are a good many APM agents where the EM is adding %1 to the name. This also shows up in the APM investigator.
The APM agent log has a warning message about changing agent names:
5/18/14 12:21:27 PM EDT [WARN] [IntroscopeAgent.IsengardServerConnectionManager] The Introscope Enterprise Manager rejected the requested agent name ("ABC1P/abcServer2"). The name has been re-assigned to "ABC1P/abcServer2%1".
Based on current analysis, this issue is a regression from the automatic metadata cleanup feature that was implemented in APM 9.5 release.
This behavior is fixed in the APM 22.214.171.124 release.
Workaround (if not on APM 9.6):
Add the below property to IntroscopeEnterpriseManager.properties file on all Collectors and restart the EM.