That the opening price on CBSH was 39 3/8 after closing at 39 9/16? I can find no trades between those prices, which would indicate that the stock was marked down on the X date.
This also happened on the last X date, equal to the 5% stock div. we were given. With no trades it would seem that the marketmakers are immediatelly taking back our dividends as their own, or that the bank is paying us with our own money.
You've got it right. It makes sense if you think about it this way. Take the 5% div. the MM's automatically adjusted the closing price down by 5%. If they didn't it would look like the stock dropped 5% on the open when in fact you just have 5% more shares.