There are several different scenarios which could be related to unexpected snapping behavior it would be difficult to list them all. In my experience the culprit is normally a smart curser setting is on or off in the snapping palette (formally known as constraints palette), but every case can be slightly different depending on the project or the end users computer setup.
I recommend contacting technical support by phone: 410-290-5114 or by email: firstname.lastname@example.org. They would be able to assist you better because there are several questions needed to be asked in order to narrow down what setting could be turned on or off. I will however list a few troubleshooting techniques.
1. Make sure 'Snap to Grid' is turned off and 'Snap to Object' is on in the snapping palette.
2. Make sure you are in a Top/Plan View then go to View > Align Layer Views to make sure all of your layers are in the same view. Example if you are working on a layer in Top/Plan view and trying to snap to objects on another layer that is in Top or custom view you may get unexpected snapping behavior.
3. Check your tool modes and make sure you have the correct mode selected for the tool that you are working with.
4. Zoom in on the area you are working in. The closer you zoom the more accurate you'll be. The snap loupe command can also be used for this "Z" Key (2009 and up).
5. For jagged lines make sure Anti-aliasing is selected in the VW Preferences under the display settings. Tools > Options > VW Preferences.
6. Pay attention to your smart cursor cues as VW is giving you visual feedback on where your cursor is located on screen. It is important to know how VW sees your cursor location vs. how we as humans see it on screen.
7. Layer scales if you are working on a layer set to 1/2" = 1' and trying to trace or snap to objects on another layer with a different scale you will get unexpected snapping results.
8. Also in the VW Help refer to Setting Snapping Parameters and Interactive Preferences (Note the difference between the Selection Box vs. Snap Box). Note that at the bottom of these Help articles there are additional links leading you to articles to help further explain these settings. Before configuring the snapping palette you will want to have an understanding of these settings or else you will get the unexpected snapping behavior and waste more time in frustration than reading first. I hope this helps.