An error code (indicated by a continuously flashing red/green LED) can indicate one of two possibilities.

Strong reflection in front of the antenna - no beep

In most cases, an alternating red/green LED indicates a strong reflection in front of the antenna and you should check the surroundings of the box.

This can be anything in front of or around the Track Box, Most commonly (too much) metal, but it could be simply a person standing in front of the Track Box. You can easily test this by placing your hand in front of the antenna. The box will immediately start blinking red/green and should stop shortly after the antenna has no objects obstructing its view.

Remove everything in a minimum radius of 50cm (2ft) around the Track Box, particularly on the front side.

Fatal Hardware Error - continuous beep

If the box has no obstructions which could be causing reflections and the error code is always present then this may indicate a fatal hardware error