I had this problem the leaves were stripped and it turned out to be vine weevil beetles I found them all on the wall behind the tub that my climbing Hydrangea was in...The only thing is they lay eggs in the pots and the larvae eat the roots of the plant so that eventually dies off ...but you say yours has come back ..I've just had to treat all my plants with nematodes to try and kill off the larvae which went on to strip the roots of half a dozen plants...look up a picture of the beetles on the web and see whether they look familiar