Do the measurements on each side after all parts have been disconnected / taken away. For example 1a 2a 1b 2b are stepper driver outputs and once the driver is out of its socket, these lines should not connect to anything else, not even to each other.
Not to mention that on startup the driver outputs should be off (enable is high, =5v), and are off till chip receives a move command. So chip outputs arent of the nature to create some behavior like described.
Just do the offline (no power) of resistance measurements on the voltage lines like above. That may point to something. The experiment is only to see if the 7805 does work e.g. provides a good 5v by itself or not, e.g. with no usb connected.
Not to mention that on startup the driver outputs should be off (enable is high, =5v), and are off till chip receives a move command. So chip outputs arent of the nature to create some behavior like described.
Just do the offline (no power) of resistance measurements on the voltage lines like above. That may point to something. The experiment is only to see if the 7805 does work e.g. provides a good 5v by itself or not, e.g. with no usb connected.