How to avoid insert material falling out

After using for a period, some nozzles may be found the insert material falling out, that may because after the period, the glue wrapping the insert material became weak, a sudden knock of water may bring the insert material away. How to solve the problem? Our solution is to put the insert material in a small plate first, then punch the plate into the body of the nozzle. Feedbacks from customers show that the problem has been well improved.