Photoshop: Manually arranging tiled windows headache

I've had problems manually arranging windows in Photoshop ever since CS 6 (and maybe before). I frequently need to drag tabbed documents into new tiled windows so I can compare and contrast open files. Sometimes this works fine, but about 30 to 40 percent of the time, when dragging the tabbed document, I can't get Photoshop to give me the thick blue line that indicates it will snap the document into a new tile. This happens most often when trying to create a tile below an existing window, though sometimes is happens when trying to create a new column as well. Sometimes when I'm working with multiple columns, the program will allow me to create a tile below one column of windows but not the other. I understand the options I have under Window > Arrange, but I sometimes need manual control to rearrange windows as needed.

I thought for a while that it was perhaps an issue specific to my Mac/copy of PS, but the problem persists across multiple work computers, including a new iMac with a fresh installation of Photoshop. Please help?