I think the likelihood of you having weird CM after an O is much higher than a temp shift along with all the other signs of O and not O'ing. I've had strange CM patterns post-O too. They usually come several days after O'ing, just like yours have this cycle. In fact, I had watery CM today (though I entered it as creamy so that FF wouldn't wig out on me), and we O'ed around the same day.
I think as a general rule you should trust a sustained temp rise over wonky CM patterns, especially when the temp shift is as clear as it is in your chart and those wonky post-O CM patterns aren't quite fertile CM, as you described. That has been my experience anyway. Unfortunately, only time will tell. Don't you just hate that!