Jack Ketch (d. 1686) was a notorious English executioner under King Charles II. He kept missing! Often with disasterous consequences. No one was or is sure whether he was doing it on purpose. Lord Russell gave him 12 guineas when he was executed in 1683. And he still missed! The first chop hit Lord Russell's shoulders. Two blows later he was finally killed. When people do things like that, do their job poorly and with horrible consequences, no one is really sure if it's their fault or not. And does it really matter?
1686? I gonna guess that he had both bad eyesight, and his hood further obstructed his vision. Having an Executioner wearing spectacles would have been a bad look. Would have been a lot less menacing and would not have been taken seriously. The guillotine was used in England before it was introduced into France, and was known as the Halifax Gibbet. too bad they stopped using it in England around 1650, that might have solved the problem.
All the Kings Charles have issues...of the last two the first was executed the second deposed by Cromwell for 9 years...
There are many jobs that had better NOT be done poorly. The results of such could / can be determined very quickly.