Glissando with "portamento" playback option stops working after 7 such glissandos

The attached score contains a repeated series of glissandi, all of which are set to "Portamento" style in their playback properties. When I playback this score, it plays correctly for the first 7 of these, but after that, it just doesn't even bother to playback the starting note of any of the rest of them. Musescore 4 Portamento bug.mscz

Nothing I do seems like it can fix this. It's pretty clearly a bug.