This seems to primarily be a problem when ripping scratched/defective discs. When the encoder reaches the damaged area on the disc it stops making progress and can sit for hours attempting to get a successful read. If an attempt is made to stop the encoding using the red X button, no response is received and an hourglass appears. The app must be forcibly closed as it is no longer responding.
My ripper settings are set to "Full cdparanoia mode" with nothing else selected under that section.