I purchased Combi Baby Label Toilet Training Set and not too happy about it. The Assist. Toilet top ( potty seat with the handle) comes off easily form the main body of the potty. My baby holds the handle while slightly rocking on the potty and falls right off it (along with the potty top) :-) Is there anything can be done to attach the top (with handle) of the potty to the body of the potty more tightly ? Any suggestion from Training Set owner are appreciated