In MMA 10.4.1, there is a somewhat strange thing. In a Manipulate with one or more sliders a slider control can be expanded to expose a small InputField. Inputting a number in this InputField, and hitting Enter, used to update the slider and its output value. Immediately. Not so in 10.4.1. If you input a number in this IF, it will just be ignored. The slider and its output are not updated. Until you repeat the process. Then the new value is accepted. And further inputs will work OK. Until you make a new evaluation of the Manipulate. Then the Manipulate/IF needs another false start.
Windows 10.
Manipulate[
x,
{x, 1, 10}
]
