Quote Originally Posted by Kitwn View Post
2v strongly suggests a lack of pull-up resistors which leaves the inputs floating as Doddy has suggested. The inputs are hovering in an indeterminate state and susceptible to every light switch and cosmic particle in the vicinity. No input to any electronics should be left like this and many devices include the pull-up resistors internally, typically 10 Kohms. Some microcontrollers allow inputs to be selected as floating or pulled-up from software.
ATMEGA328 has an option for an internal 100k-ish pull-up.