I’ll try and find a definitive answer, though it might take a while.
Because the fact you’ve touched in on a bus during its journey is stored on the bus computer, I didn’t think it mattered if you touched again. You’ll still be on the list if an RPI gets on. Plus, even if it does record a new touch, you’ll still only be charged again if it’s over an hour since your last hopper fare started.
Thankfully, you don’t have to worry with a valid zip card.