Ringtones ring only once for alarms and calls in Cyanogenmod 11
In recent Android versions in order for a ringtone to repeat on a loop, MP3 and OGG files must include a label in their metadata called android_loop with a value set to "true".  If you are not using built-in ringtones (that already have this label,) your files most likely do not have this label in their metadata.

You can use a number of freeware utilities (such as WinAmp, for example) to edit the metadata of OGG files and set this flag, or MP3Tag for MP3 files.