While running through Faerun your characters might trigger cinematics in the most different places. This is a good thing. Unexpected things might happen, we get immersed and so on.

What I have sadly observed is, that these cinematics will always cancel the forced turn-based mode. For everyone! So even if only one character is interacting with the cinematic all the other will be forced out of tun-based mode as well. And - especially if your group is split up in many parts - it can be quite difficult to reengage turn-based for all of them. This can destroy a lot of careful planning, or just waste your spells.

For example:
There is a hole in a certain cave, which leads into the underdark. I used Featherfalling on the entire group and planned to use turn-based to let them all jump in one after the other. Yet the first jump triggers a cinematic in which only the first jumper appears, but still throws everyone out of turn-based, which lets their featherfall run out. Reactivating tb in the Underdark, does not reactivate it up above, which males this even more annoying.

This is a mostly only annoying example (though it can still turn out pretty dangerous, for the character that is suddenly on his own). But I can see a lot of problems in scenarios, where one part of the group tries sneaking in from behind, while the other gets into position, at the front of an encounter. If the guys in front trigger a cinematic, the ones in the back suddenly cannot react to the guys around them and might lose their surprise.

So, uhh, after all that rambling writing above, back to my point: Please don't have cinematics cancel tb-mode especially not for everyone!