The pan-tilt mechanism should track objects smoothly. If it doesn't, here are a few things to try/check.

If you are powering Pixy through the Arduino cable instead of through the USB cable, or the I/O connector, the servos are likely not going to get enough power. This is because the Arduino typically can't source enough current for the servos, and the Arduino cable tends to drop significant voltage. There are more details here on different powering methods.

One way to check if you have a power issue: if you connect only one servo - that is, try unplugging one - does the issue persist?

If unplugging a servo solves it, that would point to current draw beyond the capabilities of your USB port or cable.

Assuming you're using a USB cable to power Pixy (and the pan-tilt), the pan-tilt servos need more power than most USB devices. Using a hub is likely to result in not enough power getting to the servos. Plug Pixy into your computer directly (no USB hub).

Unplug Pixy from power/USB and gently check the pan axis by moving it back and forth over its entire travel. It should move fairly easily and smoothly. Then test the tilt axis by moving the servo horn back and forth (not Pixy!). It too should move fairly easily and smoothly and not bind on any cables.

When Pixy is plugged into the USB cable, make sure there is plenty of cable for Pixy to look up and down, left and right.

This is an obvious one, but make sure the connectors that plug into Pixy are secure and fully engaged (you shouldn't see any of the terminal posts on Pixy – each servo connector should completely cover the terminal posts on Pixys servo connector.)
It is easy to get the pan and tilt servo connections reversed. When looking at the back of Pixy's PCB, the pan servo is on the left and the tilt is on the right of the servo connector (closer to the edge of the PCB). Verify that the Pan servo is connected to the pan connector by unplugging the tilt servo and trying to move the pan axis (do this with Pixy powered-up.) If the pan axis moves freely with the pan servo plugged in, you may have the tilt servo plugged into the pan connector (and vice-versa).

Powering servos over USB is great because you don't need to worry about batteries, but there can be problems with not enough voltage reaching the servos. USB cables aren't all created equal – some have flimsy-gauge wire that can cause problems. The USB cable that came with your Pixy has good current-carrying ability, so use it if you can. Otherwise, use a good quality cable that is 4-ft or shorter.

If the rectangle changes shape rapidly or you see lots of rectangles (detected objects), Pixy will have a hard time tracking. You should probably re-teach. Or you may need to adjust some parameters – consult this guide to learn more.

Bring up the console in PixyMon by selecting View➜console. Then hit the stop button (upper left corner of PixyMon). In the console window type this, hitting <return> after each line:

rcs_setPos 0 1000
rcs_setPos 0 0
rcs_setPos 1 1000
rcs_setPos 1 0

The first two commands should move pan servo back and forth. The last two commands should move the tilt servo up and down. Are the servos reversed? If so, reverse the servo connectors. Is the movement smooth and rapid? If not, try removing one of the servos and measuring the voltage at the exposed servo connector with a voltmeter while exerting torque on the other servo. Refer to the picture below for the servo connector pin-outs.

The measured voltage should be 4.9V or above with the other servo under load. If the voltage is less than 4.9V, investigate your power source's voltage and its ability to deliver at least 500mA.

Regardless, send us an email describing your experience (support@pixycam.com).