In the previous post I described the issue I had with routing instances and DHCP-relay, and how I fixed it. It turns out that DHCP-relay wasn't my only problem. Turns out that syslog also stopped at the time I implemented the routing instances.
To solve this I needed to inject the route to my syslog server (Splunk) in the global routing instance by using policy options.
set policy-options policy-statement syslog-policy term 10 from instance DEFAULT set policy-options policy-statement syslog-policy term 10 from route-filter 192.168.20.0/24 exact set policy-options policy-statement syslog-policy term 10 then accept set policy-options policy-statement syslog-policy then reject set routing-options instance-import syslog-policy