Hey girl friend, PirateDaisy is right about using capitals for the third or fourth time you need to use a word. But I think I can help you with the times you are not seeing the error flash in red. I found out the hard way myself.
Although we were taught proper writing was to leave two spaces after a sentence, you cannot do that any longer in VMK. Try looking at where you ended a sentence and started a new one. Bet you used "proper grammatical" two spaces! This also applies to anywhere you use written language on VMK now.
I try sometimes to "provide a little space" if I am trying to point something out. IE: "she said back to me.......This won't be good". Now, you are forced to do it as "she said back to me This won't be good".
Not sure why they won't let us use more than literally one space between any two letters/characters, but that is the reason for many of my "error messages" when I type in VMK now, when nothing is highlighted in red.