My Satmap Active 20 (which I think is brilliant!) has both physical buttons and a touchscreen with touch buttons. In normal use, the touchscreen is perfect, but in rain it can go a bit haywire as water drops can be mistaken for touches. So when it rains, I deactivate the touchscreen option and just use the physical buttons.
Actually, one of the main reasons I stopped using OS Maps on my phone to navigate was my frustration with it often going crazy in the rain. Getting a handheld GPS with real buttons solved the problem!