What am I doing wrong? Why does a midi file drop on a "between value" when the grid is something else? The smart grid should only work with the time value that is being displayed, right?

Is this a self generated MIDI file or from a MIDI Loop from a library, you could try toggling the Snap to and Snap by switch.

The file is from EZdrummer midi library. This kind of grid behavior has happened many times before. Haven't tried the snap by / snap to switch. I'll give it a go. 

The fact that it is from a library could be the source of the problem.  As you have no doubt noticed the MIDI is not spot on the grid, this is of course intended as it lends that real drummer feel, however it can cause problems when a beat is not right on the x.0x.000 of a beat as Sonar will make a best guess as where to place it.

I suddenly remembered I got this sorted out and might be helpful to share if someone else is wondering.
 
Sonar seems to snap the clip based on where you click. If you click and drag from the clip start point the clip snaps to closest value to start point. BUT.. if you click close to the ending point Sonar snaps the clip by the ending time.