I have committed this inadvertently when I was doing my thesis. I misattributed a quote to a different author. One of my panelists was able to catch this (because he was part of the original study) and he told me that the original authors should be the one cited. I was able to correct the manuscript before submitting it to the college.
Sometimes, I also quote from authors and attribute it to them but I forget to put the quotation marks to indicate which parts I quoted.