Looking at this photo below, you can see that tie starts on one diamond and finishes being tied to a completely different diamond. This is a major tying mistake made by many installers and companies. The large gap between the bottom of the top rail and the bottom of the tie where it wraps onto the fence can eventually cause the tie to slacken, easily be cut off or be untied easily.
The tie should tie off to the same diamond that it is hooked to thus keeping it tied tight to the rail. In the following picture you will see how the tie should be properly installed.