Yes, muck-ups on paper happen as well, but there it is usually not as all encompassing as with an EFB: on an EFB one typo can influence both THRUST and SPEED results. With paper, the work is divided into steps, often leading to too low speeds, but correct amount of thrust, a less deadly situation.
Bottom line is proper training and discipline in procedures.
With a computer, often the result is blindly accepted, because computers are so much more precise than human beings with paper tables and graphs .....
The benefits may be presented as enormous by the guys wanting to sell the equipment, but the negative benefits are of course not highlighted by those salesmen.
Don’t get me wrong, I like EFB’s, but they are not a godsend.