Did Shakespeare commit mistakes in his use of English ?

 It will be our mistake if we say that Shakespeare committed mistakes in his use of English. 

Difference between Shakespeare's English and Modern English.

Language must have changed in the course of a long time. Elizabethan English shows the style of old English. I.E. inflected English had case-ending for the nouns, terminations for the verbs, and the like. by the end of the 16th century, most of these inflections had ended, though some remained as it is, and the influence of the earlier inflected stage still affected the language. often when we interrogate into the history of some Elizabethan idioms which seem to us curious we find that it is a relic of an old usage.

there are numerous cases in the poet's works where a verb in the present tense has the inflection- s, though the subject is plural: cf the following lines in Richard II,

"These high wild hills and rough uneven ways

Draws out our miles, and makes them wearisome."

The verb 'draws' and 'makes' appear to be singular: but probably each is plural, in agreement with its plural antecedents hills and ways: s-es being the plural inflections of the present tense used in the Northan dialect of old English. In the southern dialect, the inflection was eth: in the midland en. when Shakespeare was born all three forms were getting obsolete: but all three are found in his works, eth, and en very rarely, es or s many times. 

A dramatist makes his character lively, and tells his story through their mouth: he is not like a historian who writes the story in his own words. the English of a play which meant to be spoken must not be judged by the same standard as English of a History which is meant to be read. for considering how much more correct and more regular in style. in speaking, we begin a sentence one way and we finish it another, some fresh idea striking us or some interruption occurring. speech is liable to change constantly as swiftly turns the thoughts.