A tunneling candle can definitely be a problem! A candle can tunnel for multiple reasons.
The most common reason for a candle tunneling is due to burning a candle improperly. Normally, you should let the candle burn long enough in each sitting to melt the wax all the way across the candle. If you don't let it melt it all the way across and blow it out it solidifies and leaves an indentation in the wax. Repeats of this cause a tunneling candle. It generally takes at least 1 hour to melt the wax all the way across.
One way to fix a tunneling candle is to get the wax to a level that the flame can melt it all the way across the diameter of the candle. We have two common suggestions for this:
1) Scoop the higher wax out with a spoon or a butter knife until the flame can melt the wax evenly. The wax removed this way works very well in a small container in the bathroom to keep it smelling awesome!
2) You can take a hair dryer and melt the higher wax on the side so it settles to a more even surface.
Before you try these steps, take a top and side view photo of your candle.
If neither of these helps get your candle burning properly then we need you to send our CS team the pictures of your candle so we can have a clear view of the issue. The more pictures we have of a tunneling candle, the better prepared we can be to assist with a solution.