If I set it to 2 columns then it seems it shouldn't have let me drop it in the 3rd column. But since it did, I don't see why it wouldn't let me drop it back where it originally came from.
In any event, again assuming I had it as 2 columns, then either it shouldn't have let me drop it in the 3rd column, or much better, pop up a message asking if I want to have a 3rd column. Another solution would be to just automatically make the layout 3 columns wide if I dropped it in a 3rd column.
Just BTW, 2.3.9.147 did not fix the problem of tiles moving and not snapping back when being dragged in a browser, which we can't do on an iPhone. But, on phones, and not in a browser, editing the dashboard brings up left/right up/down buttons (though it is a bit awkward to use and the arrow controls cover much of the label so I'm constantly toggling in and out of edit mode to see where the control I want to move is located).
I also wish there was a cancel button as I sometimes mess up trying to set a layout and it would be easier to start over.
I am running 2.3.9.158 and drag and drop on legacy dashboards doesn't work for me any more. It used to, but now when I drag a tile to a location it just falls where it feels like it.
@bobbyD - I'm curious if the subject matter in this thread is on the "to do list"? I can't figure out the rhyme or reason to what makes a particular spot on the grid available for dropping - here are pics of the original display along with the available slots and then a second pic after I move and as others have pointed out, I can't even drag it back to where it just was.
For posterity, I have figured this out. You have to click the sprocket in the top right and increase the grid size. The dashboards let you move things outside of the defined grid with the directional arrows (the way we used to have to move tiles), but to drag and drop, the defined grid needs to be larger.