One possibility is that the touch surface is already registering contact.
This may be a dirty surface but I would suggest checking the plastic surround for either deformed plastic pressing down or maybe dust/crumbs caught in the gap.
I have a related issue at the bottom centre of the screen where I used to roll my finger over the edge of the plastic to press the button to change to "Accessories" mode. I would subsequently have unresponsive buttons or the mode would randomly change back to the loco screen as if the button was pressed again - because the plastic was bent onto the screen.
Regardless this does not render the CS1 useless - connecting to a PC can allow continued access to almost all the functions
like registering new locos, signals and routes manually (and , with the right program, can make the process smoother and more fun)
Peter
