The game's UI is deliberately set against you and goes out of its way to sabotage your actions.
Misty step is a good example - You'll highlight somewhere with Misty Step, and it'll tell you that it's a valid destination... but what it doesn't explicitly warn you about is that back where your character is it's determined that the correct way to do what you're asking is to walk two steps away from the nearby enemy, then teleport... so you click to do it, and presto, you take an OA.
Even something as simple as 'move around to the other side of this enemy', if you simply try to do it in one go, will *Usually* result in the game deciding that what you want/need to do is walk away from the enemy, provoke an OA, then walk back in close to them on the other side.
The control UI is actively your enemy in this game and you have to fight it, non-stop, to do what should be simple.
In terms of enemies getting OAs at incorrect times, this is a bug in the system that they've still not managed to correct, and it's worth reporting with their bug form whenever you can give them something substantiated or replicatable. The most common way this shows up is moving away from something, and it only realising later that it could take an OA, sometimes as late as the next action. The later it goes before triggering, the more chance of it canceling and negating what you did between then and now. Again, whenever you have this happen in away you can replicate with a quick load, it's very much worth sending them the file with the formal bug form.
