Idea for minimising leaks into mouth -
Those carts that have a seperable end piece (such as the 901 ones I have) - insert a little cotton wool inside to catch any liquid leak; not so much as to restrict air flow though. If inhale does get hard because the cotton wool has become soaked, carefully replace it.
This might loosen the tight fit of that cap though so if it does become too loose, replace the cart.
Those carts that have a seperable end piece (such as the 901 ones I have) - insert a little cotton wool inside to catch any liquid leak; not so much as to restrict air flow though. If inhale does get hard because the cotton wool has become soaked, carefully replace it.
This might loosen the tight fit of that cap though so if it does become too loose, replace the cart.