I have a backup of the Dorchester executable, and Snap To/By groups of notes works as expected there as well, regardless of the docked/floated state of the PRV.
 
I think we need a recipe that starts with the default Normal template that ships with Platinum, keeping in mind that the PRV-specific snap mode defaults to "By" in the Normal template.
 
 

Just to experiment a bit, i docked a PRV window, set snap to at 1/4 in both Track view and in PRV, made sure snap was on.    In fact if I zoomed in, and laboriously brought a note to within 10 ticks of the quarter note grid line, it would snap as expected.    
 
But!! Note Entry: the snap works all too strongly:   I positioned the cursor at 479 ticks away from the quarter, and the damn thing snaps all the way back to the quarter grid line. 
 
And to clarify, the same thing happens with one note selected as with multiple notes selected.
 
Then I changed the snap setting to 1/16 (240 ticks) ... now I'd expect snap to happen if I drag a note to with 1/64th (60 ticks) ... but the same thing: the note had to be laboriously brought to within 10 ticks of the 1/16 grid line.     And the note entry snap happened at one tick away from mid-point!  (239 ticks)
 
But I work on a 10 minute, 100 bar, 400 quarters, 384000 tick, basis -- could this be the difference?   For me, "near" the note, if I want a snap at such a big resolution as 1/4, the snap should happen if I'm within 1/8 or so (240 ticks) of the grid line.    I usually use "snap", if at all, at 1/64 or 1/128, in order to avoid getting too many controllers with a controller draw.   
 

It sounds like you have your snap intensity set quite low. But I think it's working as intended that note entry snaps to the grid regardless of snap intensity. Only moving notes honors snap intensity. This allows you to work quickly when entering new notes without having to aim too carefully. If you want freedom when entering notes, just disable snap.

williamcopper
Just to experiment a bit, i docked a PRV window, set snap to at 1/4 in both Track view and in PRV, made sure snap was on.    In fact if I zoomed in, and laboriously brought a note to within 10 ticks of the quarter note grid line, it would snap as expected.    
 
But!! Note Entry: the snap works all too strongly:   I positioned the cursor at 479 ticks away from the quarter, and the damn thing snaps all the way back to the quarter grid line. 
 
And to clarify, the same thing happens with one note selected as with multiple notes selected.
 
Then I changed the snap setting to 1/16 (240 ticks) ... now I'd expect snap to happen if I drag a note to with 1/64th (60 ticks) ... but the same thing: the note had to be laboriously brought to within 10 ticks of the 1/16 grid line.     And the note entry snap happened at one tick away from mid-point!  (239 ticks)
 

 
Snap in Sonar activates based on the distance from the grid in display pixels not ticks.  Tested this by using different zoom levels and screen captured the activation point.  An image processing program indicates that the distance is approximately 12 pixels on my system regardless of the zoom level.
 
The use of pixels for snap strength is common.  For example, another DAW I use has options to set the grid with note values and set the snap strength in pixels (not ticks).
 
The bottom line is the more the track is zoomed in the closer the note has to be to the grid in ticks.
 
-- Ron
 
[Edit]  The measurement of 12 pixels was made in the PRV only.  Track view distance was not confirmed.  [/End of edit]
[Edit2]  The Snap intensity in preferences was set to one mark below "Extreme" and the grid was set to quarter notes.  [/End of Edit2]
 

This has nothing to do with pixels. Here's a capture. The whole time I'm moving the mouse evenly first to the left, then once it snaps, evenly to the right, never stopping until the notes themselves stop moving.
 
In the Control bar, Snap is set to "To" with a note value of 1/8 and marks disabled.
 

edit: Reproduced in Everett.

yevster
In the Control bar, Snap is set to "To" with a note value of 1/8 and marks disabled.

 
The snap setting in the Control Bar doesn't need to be set to "To."
As I said in my last post, it's the option in the PRV that decides the behavior.
 

Unfortunately the video isn't smooth so I can't tell where it's snapping and where it's just pausing. It appears that the start times of the individual notes are inconsistent; if so, that could be an issue. If you select multiple notes, SONAR might not know which note is the one that's meant to be the "master" snap.

Icontakt nailed it. So the PRV now has its own "to" vs. "by" setting. I got confused by the fact that the Control bar Snap toggle does enable/disable the PRV snap toggle. I will resist the instinct to blame the software design when I get confused. 

I agree it's confusing. The To and By should be visible without having to right-click on the drop-down. 

yevster
Icontakt nailed it. So the PRV now has its own "to" vs. "by" setting.

See post #11: "the PRV-specific snap mode defaults to "By" in the Normal template."
 
More proof that a picture's worth a 1000 words. 
 
Glad you got it figured in any case.
 
Incidentally, I did report to the Bakers when PRV To/By was first introduced that having it hidden and defaulting to By was going to cause a lot of confusion.