Some glissandi get "stuck" holding the original note indefinitely

I've noticed this several times as I'm arranging for SATB vocals. If I use a slide-out, a fall, or other similar glissandi (even a gliss. set to "portamento"), in the playback, the original note never stops playing--even many measures later, including after rests, and over other notes on the same instrument. It's proven incredibly frustrating as I have no choice but to delete those markings from my scores just to preserve the playback.

It seems this issue is only affecting voices--other instruments' playbacks work perfectly fine.

I've attached a dummy file which should demonstrate this issue.

To recreate:
1) Create a track using any vocal instrument
2) Add a note that has a slide-out, followed by any amount of rests or other notes
3) Playback. The original note will not cut off until it is played again in the same instrument.

If you have any questions, or if you are unable to recreate this issue, please let me know. I sincerely hope I'm not the only one experiencing this.