Hi, and welcome!
It may be a character code default issue
paste("This is text cut and pasted from a plain text editor on a Mac that includes the single quote mark, '")
#> [1] "This is text cut and pasted from a plain text editor on a Mac that includes the single quote mark, '"
Created on 2019-10-25 by the reprex package (v0.3.0)
What's your system, and can you provide a reproducible example, called a reprex?