Logs: https://mclo.gs/9ZgV7xX
Running /sparkc profiler start immediately after going into a singleplayer world claims that the profiler has already started in the logs, /sparkc profiler info and /sparkc profiler stop both claim that there isn't a profiler running.

When running spark on an integrated server, you'll need to stop the server background profiler /spark profiler stop before starting the client /sparkc profiler start