The most common reason for this problem is squirrels.  They will chew off the candles looking for nesting materials.  If you have several squirrels, that could be the answer.  However, if it continues and you don't have a squirrel problem, you should have a certified arborist come out for an inspection.  You can find one by going to this link and clicking on Find An Arborist.  Put in your zip code when prompted and a list of certified arborists in your area will appear.  https://www.treesaregood.org/