Grammar Meltdown

Sometimes it’ll mark words with that green grammar line, telling me the word at the beginning of a sentence needs to be capitalized. The only problem is the words are at random points in the sentence, and it’ll only highlight part of the word, not the whole thing. There’s also usually not any kind of punctuation before the word, which makes even less sense. I’ve never had a writing software that did that, and I have no idea why it suddenly started doing it. I’ve also got the latest OS X software update, if that helps at all.