Mac: Last Character Sometimes Cut Off

Hi,
Sometimes when I am using DownArrow to read text line-by-line in Safari, and the line is long enough, VoiceOver does not speak the last character of the line. I have noticed this occasionally in Mail, too. If I examine the ends of those lines, the last characters are there. Any time I read chunks of text by using VO+RightArrow, VoiceOver reads all of the text. How can I fix this issue?