I have reported this during the beta phase, but I still have this problem in the official release of Resolve 15.
Whenever I create a background node in the Fusion page and try to view it, Resolve crashes immediately.
This also happens when I merge the background node with any other node and try to view the output of the merge.
This happens on my CentOS 7 machine. Haven't tried on any other platform to see if I can replicate the issue.
Here are the logs from my system.