Well this seems weird. I have used G602 and that never had any problems whatsoever. Anyways, here some common fixes that will help you resolve the issue.
# Clean your mouse and connect it to a different port.
# Update your mouse driver from the official website of mouse brand.
# Check for remote control software.
# Use [link|https://cpstcounter.info|CPS counter|new_window=true] to test mouse buttons one by one.
# Disable the touchpad for Laptop users.
# Disable the ClickLock feature (for Windows PC).
I am sure at least one or two steps from the above will help fix your Logitech G602. If not, just ping me up!