From my understanding, this maybe due to the opposite characters of sealants and tufoil. No doubt, it's best to find a permanent sealant solution rather than temporary. Just that if anyone has tried using both at the same time, I am curious to find out if they have the same result.
I also notice that after using tufoil, there seems to be a metal 'ka-ching' sound whenever the clutch or accelerator pedal is depressed, is this normal?