The A3D product trackball relies on a clean connection to the internal rollers for proper tracking. Over time, the buildup of finger oils can cause slipping in this connection.
Your A3D product is a precision instrument, when you first opened the package and hooked it up it was probably smoother than it is now. It probably seemed to be more precise when turning and looking around. What follows is a little information on how to clean it and get it back to that new feel.
I think the place to start is a visual inspection. Remove the retainer ring, that is the red ring with two little holes at the 3 o'clock and 9 o'clock positions. You will need to rotate the ring 90 degrees counter-clockwise, this will put the holes at 12 and 6 o'clock. The ring should now come off with little or no effort. Do not force it, if it does not want to come off verify that the little holes are at 12 and 6 o'clock. Turn the unit over and give it a little shake, use your other hand to catch the grey trackball when it drops out so as not to mark your desk.
Let's take a look inside, You should see three, metal roller bearings. These bearings should be shiny with no visible sign of grease, hair, dust or gunk on them. If they are dirty you can use your finger to roll out the hair and lint. Make sure that you remove all lint and hair and ?? (what is that stuff anyways) from the sides of each bearing. If there is a buildup of junk on the sides the bearings cannot roll smoothly and may even be locking up and making your movements rough. The surface of the bearing should be shiny and smooth, if not try rubbing it with your fingernail or "Exacto" knife. If you seem to be able to clean it up, continue and try to get as much of the gunk off as possible. You can also use those green scrub pads "Scotch Bright" (make sure it is dry) and lightly rub each roller to get it as smooth as you can. After these bearings are cleaned up you should be able move them with your finger and feel no resistance. The bearings are sealed so if you think hitting them with a drop of oil will help, it will just get spread around and probably stop the rubber rollers from making a good contact with the trackball. In other words don't do it.
Which brings us to the two rubber roller assemblies. These rollers are connected to a shaft that is being pushed against the trackball by a small spring. You need to remove all the hair and gunk from the shaft using any means possible. I find that tweezers work well and sometimes a mini vac. Do not try to blow it out with compressed air, all this does is spread the gunk & junk around the inside of the unit and will require you to clean it more often. While you are working in this area we want to check out a couple of things. After you have the hair and junk cleaned off of the rollers check out the spring (it is a little bar that appears to come from above and rests on the back side of the shaft). The spring should be pushing the shaft towards the center of the unit, give the shaft a little push out and watch it come back in. It should spring back in as soon as you stop pushing and rest against the stops. If the shaft does not come back into the stops your spring may be weak. If you are the careful type, you should be able to grab the spring with a pair of small needle nose pliers and give it a little tug towards the center. It does not need a lot of pressure pushing it in but should not be slow to return.
The rubber rollers themselves have a tendency to collect all kinds of junk or gunk or just plain stuff. These will need to be cleaned thoroughly. I suggest that you use that "Exacto" knife (carefully) or your fingernail to scrape off the crusty stuff as well as you can. Once it is pretty clean you can wipe it clean with a little bit of rubbing alcohol on a cotton swab. Make sure that your swab is twisted tightly so no cotton threads come off onto the shaft. Once the rubber rollers are clean, it will kind of stick to your fingertip.
Tuning and spacing. Let's take a look at that shaft again, and make sure the rubber rollers are spaced properly. Push in the shaft and watch how the spring will get closer to the rubber roller. You want to make sure that the rubber roller is as close to the spring as possible without touching. Ideally the rubber rollers should be placed at 6 o'clock and 9 o'clock. Due to the differences in springs it may not be possible, but get them as close as you can.
Last but Most Important !
Clean the Trackball with a lint free cloth moistened with a little rubbing alcohol. It really surprises me how often you will need to clean the unit if you put the trackball in dirty. It will help if you wash your hands before you use the Assassin 3D. Most of that gunk you just cleaned off comes from the body oils in your hands.
Oh... One last thing....
Never eat anything while using your Assassin 3D, especially those frosted "Circus Cookies" and Milk. This can cause it to start slipping and require cleaning after about 5 min. 8^}