On the iPhone 6, when you complete an objective, the progress box pops up and blocks the rush button. This is particularly annoying when you have an objective for collecting resources because you have to either open/close the objective window or wait for the window to disappear before rushing.

I play on a 5s and it's the same here...obviously just a lack of foresight on devs. Very annoying when wanting to knock out objectives. I'd pay $20 for a rebuffed, richer, less buggy/frustrating PC version of Fallout Shleter...but we'd have to wait until at least next summer would be my guess.

What I do is tap on a dweller and it makes the objective window disappear. It zooms in a little so you have to click off him to go back to what you were doing, but it beats waiting for the thing to go away on its own!