Lawnmowers which cut hair? Which turn off left instead of travelling straight ahead? Which cut through your cable at the same time? Translations of operating instructions should be put into the hands of experts. Sometimes, in the field of medicine for example, translation errors can be not just amusing but life-threatening.
Above all, amateurishly translated operating instructions are also disrespectful towards those who need to read and understand them. It doesn’t matter how good the product is, inadequate instructions for their use cause the customer to draw negative conclusions about the quality of the entire product– a marketing risk which is not worth taking.