Generally, if something isn’t against the rules in the game manual, it is legal. You can descore caps as much as you would like, but if you knock the cap out of the field multiple times, you may be disqualified.
adding on to what The Electrobotz said, if you do knock a cap out of the field, a referee will put it back on the closest tile scored for the team that didn’t knock it out.
as indicated above, the cap goes to the field turned to the opposite color of the robot that touched it last. If the referee can not determined which alliance caused the cap to go out of the field, it will remain off the field.