New user - wrangling line labels

I’m done with Microsoft, so I’m going all-in on this OS X thing. This is my first non-Visio network diagram, and it’s going OK so far. I figured out stencils (and spent an afternoon drawing my library), and the layout engine is easier to deal with and get consistent results, so that’s nice.

But one thing I haven’t figured out is lines.

On my diagrams, I’ll often have an object (imagine a square) with a line coming out of it, connected to another object (square). Where it connects to each square, I’ll have a text field (two lines: an interface like “gi1/0/1” on the top line, and the IP “” on the bottom) that straddles the line. Dragging this text box onto a line anchors it to the line as a label. So far so good.

Now, instead of grid snapping, it moves continuously. This makes it a little more challenging to align with other nearby text fields, but with patience I can manage. Except when I change the line in any way – once, all I did was change the color – it moves around in an unpredictable way. Typing in a left-justified text box also seems to move its left side.

What am I doing wrong? Any way to keep these locked in place?