Have you tried to check the rollers carefully right after getting the error 2? For some reason Roomba is thinking that something is stuck in the robot vacuum rollers as they creating the resistance. If you have it for a while it might be that the inside gears are getting resistance from dirt. You can see in this video how to repair it.

Did you get genuine iRobot battery? Otherwise, suggest to check steps mentioned here (cleaning contacts, etc.): https://homesupport.irobot.com/app/answe...-charging-error-5