Can't drag elements on dynamic lighting layer

Greetings,  I've been having an intermittent issue with dynamic lighting. Per the tutorials I use separate lines for doors so that I can, supposedly, just grab the door and move it to allow the players to see through.  However, what I sometimes happens (not all the time) is that while I can select the line for the door I do not get a move/drag cursor. I only get the resize points. So I can resize or even delete the line for the door but I cannot grab or move it. Even after resizing it to make it huge I do not get the move/drag cursor no matter where I hover over the element. Is this a known bug or user error? Thanks. 

Although grabbing those elements can be tricky, you have used the most common methods of selecting that usually work. Have you (since you are a Pro subscriber), considered the Doorknocker API script by Scott C? It gives you a token that you can move around the board. It automatically detects the presence of doors (massed on the line color), and provides macros for turning them on and off. No more trips to the DL layer or grabbing finicky lines.

I was not familiar with that script. I'll look into it. Thanks.