When shuffle is checked in the playlist, it also repeats the whole playlist forever, even if repeat is not checked. The bug seems to happen as soon as there are two or more songs in the playlist.
Created attachment 6821 Fix the infinite loop when Shuffle mode is enabled and Repeat is disabled. I confirmed the problem. The proposed patch restores the expected behaviour: the playlist is played once when Shuffle mode is enabled and Repeat mode is disabled, and the playlist is looped, with a random selection, when both modes are enabled.
Julien Sopik referenced this bugreport in commit 17dcf57cb3a728651278669ad8d63ac610d1f89a Fix bug 12010. https://git.xfce.org/apps/parole/commit?id=17dcf57cb3a728651278669ad8d63ac610d1f89a
Thanks for the patch. Everything looks good here, applied above.