I have noticed problems with connector lines similar to those previously reported by krazykat and eburt. Professionally I use Visio to draw network diagrams, but on the side I enjoy drawing automobiles. I never really had any major problems until Visio 2010 came along. Now I have the problem of connector lines skewing wildly off of the drawing if an object on the page is moved. I don't have a fix, but I do have a clunky work-around.
Normally when a line is connected to another line or object, the connector point turns solid red. What I have noticed is that at "some" point, "something" triggers the connector points on "some" of the lines to change to hollow red instead of solid red. That is, the outer circle of the connector point is red, but the inside is white. Once the connector points change to this color, they are now armed and ready to distort. Moving an object can and will cause these lines to wildly distort. Specifically, many lines from all over the drawing will move and converge on an invisible connection point somewhere outside of the drawing - as if a magnet has sucked one end of the lines to it. Sometimes both ends of the lines will be sucked to two different imaginary connection points off of the drawing resulting in a large budle of overlapped lines.
The things I have found that will sometimes cause the distortion include moving an object on the page or highlighting the entire drawing and moving it using the arrow keys. Grouping a bunch of lines can also cause the distortion. If lines in the drawing have the hollow red connector points, then Copy/paste or <ctrl> + D will result in a copy with distorted lines even if the original drawing has not yet distorted. I have not been able to figure out what triggers these connector points to change state. I suspect it may have something to do with the number of lines or connector points on the drawing as it usually does not occur with small drawings. I also have not been able to figure out why some lines are affected and others are not.
After turning a fairly detailed drawing of a 1958 Chevrolet Impala into what appears to be a bag of uncooked black spaghetti spilled on the floor with a single key stroke, I decided to take measures to prevent such disasters.
My work-around #1: I always save my changes frequently when drawing. I use the key sequence <ctrl> + Z very sparingly . . . . Then I will occasionally click on random lines in the drawing to see if their connector points appear normal or if they appear hollow red. Once I find one with hollow red connector points, I know there will be more. I simply click on the offending line with the hollow red connector point and then use my arrow key to move it in any direction and then move it back to its original position. After moving the line, the connector points are no longer hollow red and the line is not in danger of distorting. One down side to this is that from time to time, I will "correct" a line, only to have its connector points change back to hollow red at some point in the future. It may be a few minutes later that I find the line has changed back to its evil state - or it may be several days and several saves later that the lines change back.
Normally these evil lines are found in clusters. If one has a hollow red connector and is touching another line, it will also be infected on the same connecting point. However, some lines are only infected at one end and when highlighted they will only display the hollow red connector on one end.
I have also found that I can highlight a portion of the drawing that contains several evil lines and move them as a group. However, if you try to grab the entire drawing and move it, the lines will distort!
Workaround#2: When I am done drawing for the day. I will <ctrl> + D to duplicate the drawing on the page. If there are problems, the duplicate's lines will show it. Then I look at which ones are distorted in the duplicate and go back up to the original drawing and "correct" the lines by moving them and then moving them back with the arrow keys. Once I can duplicate the drawing on the page with no problems, I know the lines are not infected. Sometimes there can be one or two small lines that are distorted in the duplicate that I cannot find in the original drawing. When this occurs, I group all of the lines in the duplicate, change the color from black to green or red and then move the duplicate directly on top of the original drawing. The different colors easily reveal the problem lines. Any exposed lines that are still black are "evil" lines and need to be corrected.
I hope this helps save someone some of the frustration I have experienced!