Steps I took that resulted in the problem:
draw a track, and set large mills (e.g.128)
save file or move one terminal of the track
the track become shorter and a bad joint arrangement is made
if you reduce track width, the track can also become unconnected!!!
What I expected should have happened instead:
The track remain as drawn the first time. Please fix soon because Fritzing become totally unusable!
My version of Fritzing and my operating system: