Heidi - the only time I have noticed mine leaking around the legs is if I have left it on too long - or if he's had a couple of really big drinks, done a HUGE wee - and the inserts have bunched up towards the middle - because they are sooo full - and then the next time he pees - there is nothing there to catch it... YKWIM?

So it could be something like that - especially if he is a big mover and shaker like mine is

Or the PUL might need resealing.. in which case chuck it in the dryer - that usually fixes it yeah?