This tells me that you have two Splunk process running under different users.
The daemon name is configured withing /opt/splunk/etc/splunk-launch.conf
You likely have one running from init.d (default) and another from systemd after configuring it.
Assuming this is not production, I would suggest that you try the following, in order:
systemctl stop Splunkd
(here is where you can modify the daemon name in /opt/splunk/etc/splunk-launch.conf)
systemctl start Splunkd (or the name you set within the conf file)
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