I have a 2016 Lincoln MKX. The SYNC is updated to the current version.
The infotainment system is slow to react to choices. When any item is selected (Radio, Navigation etc…) the unit takes 10 = 15 seconds to react and sometimes longer.
If the steering wheel controls are used, even longer.
The system works fine…just slow.
Has or is anyone else experiencing this? or does anyone have suggestions on how to remedy the issue?
thanks for taking look and for any suggestions
Steve
No experience with that car or its infotainment system. But that sort of problem can be caused if one of the control buttons is stuck in the active (pushed) or on position. Sort of like what happens if a key is stuck on a computer keyboard. Suggest to carefully examine all the buttons with good lighting and a magnifying glass. Notice any gunk surrounding a button, preventing it from freely moving back and forth?
Check the software date and then see if there are any updates. The update info should be on the Lincoln website. Maybe you can use Wi-Fi to update software. If not, the dealer can do it for you.
You certainly have buttons in the steering wheel, but the dashboard controls may be on the infotainment screen. Which is it? If actual buttons are sticking, you could press them all repeatedly while the car is off. If they are sticking, this might unstick them. And, no more milkshakes in the car. 
Reminds me of the time my credit card stopped working while on vacation, road trip. Couldn’t pay for anything, gasoline, hotel, big problem. I had to phone the credit card company & enter a long code to get it working again, but the only phone available, somebody had spilled a soft drink on the keypad, keys sticking like crazy. It took me a dozen attempts to enter that code… lol .
If the system reacts long after pushing the button, this sounds like a software problem, not a sticky switch.