I have the same problem (just reproduced both on Rapture Session and Kontakt libraries): in the PRV, when I click and drag a velocity bar the note is triggered, when I release the mouse the note continues forever ... even if I turn off/on the audio engine it continues playing ... it only stops when a "Note Off" message (for the same note) is sent to the VST.
 
... very annoying (I often adjust velocities in PRV) ...
 
Sonar version: 23.4.0 [2017.04] Professional

I have had these problems since the 2017.04 update:
 1) When adjusting the velocities the notes go on but do not turn off (can turn this off in prefs)
 2) For the first PRV edit only: If I select a group of notes to adjust velocities, I click on a velocity bar and the selected notes 'jump' lower in velocity by around 10 to 20 points. And if I 'undo' it does NOT undo. So the volume goes lower but I don't know how much exactly.     This happens the first velocity edit only, subsequently the PRV works OK.

Thanks for keeping us up to date!

EDIT - It seems, when selecting notes in PRV and then click on a velocity bar, the velocities jump sometimes down, sometimes up. It won't Undo.  It seems this can happen at any time in the PRV.
  
                

The bug with velocity bars has not been fixed in 2017.05.

Thanks for the update.
I'll be sticking with 2017.01 until reports of 2017.06 come out.