Consider the following diagram made with dia 0.97+git (0.97.3+git20160930-8):
The line (actually an arc) between the circles should not protrude into the circle (left side) and should connect fully with the circle on the right hand side. This problem can be a lot worse than this in a more elaborate diagram, going half way into the circle, and so on. I find it highly unlikely this a user mistake, I've used the tool for years and tried multiple times to connect the arc in different manners. It looks like a display fault.
To reproduce: Place two circles and connect an arc between them.
This is on Debian, using libgtk-x11-2.0.so.0, libgdk-x11-2.0.so.0
I tried installing the older version available with apt-get, 0.97.2-8 (/var/lib/apt/lists/ftp.us.debian.org_debian_dists_wheezy_main_binary-amd64_Packages) but it throws a segmentation fault.