This one is hard to explain but the issue is that in piano roll, if under View--> Grid Resolution --> Follow Snap Settings the grid lines not only do not snap to the Snap settings in the menu bar but are inaccurate. 
 
Steps to repro:
1. set Snap on and to 1/8 and turn Smart Grid on
2. open piano roll, in view -- grid resolution, set to 1/8. 
grid lines switch okay and are at 1/8
3. Now switch grid resolution to Follow Snap settings
4. Grid lines snap to 1/4 triplet (they should not switch at all yet since Snap settings are still 1/8)
5. Use track zoom tool to widen snap to 1/16
6. Notice grid lines do not change to 1/16 and remain at 1/4 triplet. 
 
I may not be understanding how this feature works. Any advisement would help.
 
Another problem I'm having that I'm writing something in triplet (4/4 meter) so I have Smart Grid turned on and I select the triplet button in the menu bar. But every time I use track zoom, it disables the triplet. Does Smart Grid not maintain the triplet snap settings when zooming?  I understand that I can disable Smart Grid but then I have to constantly manually set the snap settings. And when I'm going back and forth from Piano Roll to Track view, this gets very tedious.  
 

smart grid adjusts the snap settings and grid based on zoom level.  disable smart grid and bind hotkeys to snap settings.  

Thanks Swamptooth, not sure exactly how to bind hotkeys to snap settings. The issue is why Follow Snap Settings don't work in Grid Resolution. Seems broken. 

I'll check tomorrow. This was broken off and on through updates x1-x3 it may have snapped again...
You're talking track view or prv?

Gotchya. Everything in Track view works fine. Grid lines reset to snap settings when using track zoom. 
Prv is where it's not working properly.  
thanks for looking into it!