Before revision:  Moreover, in addition to the robots' own imperfect models, day-to-day operations entail various sources of errors that , despite small, rapidly accumulate as tasks change and robots are re-programmed, often requiring time-consuming calibrations.
After revision:  Moreover, in addition to the robots' own imperfect models, day-to-day operations entail various sources of errors that despite being small rapidly accumulate. This happens as tasks change and robots are re-programmed, often requiring time-consuming calibrations.