Lacking playback on glissando for Muse Sounds electric bass (among other instruments)

I tried placing a straight glissando on an electric bass with portamento playback.
Playback overlooked it and just played the two notes individually. I tried it with other plucked string instrument sound fonts, and it only worked on some (like the fretless bass). I also tried other playback types like white notes or diatonic, but it seems the only thing that changed whether the gliss was played back or not was the sound font.

Any tips?