MLBM 2016 properly stops you from trading after the deadline, and properly stops you from making roster moves during a playoff series -- If you try making a trade on 8/1, you are told you can't make trades after the deadline. And of course, during a playoff series, if you try to activate a player, you are told you can't change the roster during a series. So far, so good.
BUT...
You can make a trade during a playoff series, and the acquired player will appear in your playoff roster! Just as an example, I engineered this trade during the World Series with the team I was playing against!
As you can see, it's game two of the World Series.
And Bob Ramey is my starting CF:
Yet I am allowed to trade him, and if I had gone through with it, Cahill would have been put on my active roster -- during a playoff series! (I have actually done this in iOOTP!) This should be fixed, and the easiest way would be to put a complete freeze on trades between 8/1 and the end of the World Series.