All my boys have done this
I get so sick of putting nappies back on, that is after I have found them

Nothing worked here not even draw string woolies they would just un do the nappies some how and they would come off still with the woolies or pants over the top..........Actually Coby came home from dancing with just his longies on last Wednesday.....His itti bitti NEVER to be seen again
So this has always be the beginning of TT here
Good luck...... hope you find something that works because 4 boys later and I never have