I was doing a 2 days project, about 10 hours each. Mostly recording bits of midi and some audio, but spend time on editing a lot (cleaning up midi, shifting notes, and also quite a bit of Session Drums programming), especially on clips - copy/paste, shift.
 
I've experienced losing the Snap to Grid function twice. I can toggle the function, but I cannot set the Snap Value (such as Whole, 1/2, 1/4, etc..). These values are simply missing from the tool bar. When you click on this option, the common pop up for you to select Whole, 1/2, 1/4,etc.. would simply not open. Regardless of the Snap toggle on/off, the clips simply won't snap.
 
Closing X2a and opening it immediately solves the problem.