CPU usage in the background

I'm having a weird issue where Darkroom keeps doing something in the background after being minimized / closing the window and doesn't seem to stop.

To reproduce: Open any image and close the darkroom window, cpu usage for the darkroom process will hover between 20-40%.

If I go back to the library view and then close it, it jumps back to 1-2% which is negligible, but still unnecessary.

Could rendering / whatever processing that happens be paused if the window is minimized / closed? Since macOS keeps apps open after closing the window it's kind of annoying having to explicitly quit the app from the dock every time (and I usually forget it too and battery tanks)