Part of the bounding box does not show up in 2019 Illustrator CC. How to fix?

Hello, I've been using an old CS3 Illustrator and recently upgraded to 2019 CC! I notice that part of the bounding box is not showing up when I am using a simple line (pictured). The middle box only shows up if it is any other shape than a simple line. I usually grab the (missing) box so that I can hold alt/option (on mac) while dragging so the line evenly lengthens on each side. The problem now when I grab one of the corner boxes instead of that missing middle box is that while the line grows, the line does not stay in the exact position and it moves up or down slightly. This creates an efficiency issue for me because now I have take the time to again place where I need that line to be.

Any resolution for this to get that middle box back?

Thank you for any help!