In this image you can see the blueprint preview going over the left edge of the tooltip:

In this image you have to look close but the preview goes over the top left corner of the tooltip:

I run the x64 Linux version of Factorio. Although I have a number of mods installed in that game I doubt that they are causing this problem. I didn't include a save since mine is ~46 MB (nearly all in level.dat). If you have difficulty reproducing the bug I can try and upload the save someplace.
Steps to reproduce:
1. Make a blueprint large in both dimensions such as an entire endgame base.
2. Look at the blueprint tooltip and see the preview going over the left and or top edge.