MS4 portamento gliss problem

[IBDense]

A gliis using portamento gives strange results. I'm using the setting
MS4 Portamento problem.zip

listed under the Playback properties as portamento (last option) but it’s still playing 11 notes including start and finish from C4 to C5. Just the two notes gives me a sound like wawawawawawawawawawawa climbing legato-ish from C4 to C5
If I change the notes to C4 to C7 I get the wawawa sound with what sounds like 4ths or 5th and them after the 10th one it jumps way up to C7.
I'm using the MS Basic/Synth/Lead/Sine Wave.

Included MS4 file and screenshot...