.
image for explanation, click to enlarge

Hhm, I can't seem to reproduce your scenario where the bbox corner snaps to a grid line and not a grid intersection. Which options are selected in your snap control bar?

I guess the first thing is to make sure that only "Snap bbox corners" and "Snap to grid" are selected on the snap control bar.

Is that a raster image that you're trying to snap? If so, then it looks like you have a pixel grid?

Oh ok, I figured it out. Well at least I discovered one situation where this could happen. In my Document Properties, I have Snap to Grid set to Always Snap. That makes what I call a very strong snap. If I change it instead to "Snap when closer than" and make the distance 1 (which makes the weakest snap), AND I'm zoomed in far enough, I can make the bbox corner snap to a grid line. If I'm not zoomed in very much, it can't happen. So you may be able to avoid snapping to the grid line, by not being zoomed very much, and not have to change the settings in Doc Prop.

There may be some other situations where this could happen, I'm not sure. I haven't discovered any others, although I'm not the snapping expert And there may be a snap distance where you can avoid it snapping to the grid line, and still not have it set to 'Always snap'. You'll just have to experiment.

Let us know if any of that solves the problem. There may be other or better solutions

What Brynn explained was correct, so please check if "always snap to grid" has been enabled in the document properties. It should be enabled by default though. If not, then snapping will only occur when you're within the maximum snap distance, but this is measured in screen pixels (as opposed to document pixels).

However, another reason could be that you're moving the corners or handles along a constrained line, for example purely horizontal or vertical. This happens when stretching or skewing an object. In this case Inkscape looks for intersections of the line along which the movement is constrained with lines of the grid. In general this will not snap to grid intersections. If you need to snap to grid intersections in this case, then you could use the corner (scaling) handles instead of the side (stretching handles), or you could try not-pressing-the-control-key when translating an object.

dvlierop wrote:... snapping will only occur when you're within the maximum snap distance, but this is measured in screen pixels ...

Oh, I see. That explains a lot. I thought that snap distance in document properties is for document pixels, because it's called "document properties". I've set it back to 20 from 10 and now it's less snapping to lines and more to intersections of grid, thanks.