It's a problem with the phone really. This "System UI" is supposed to be the standard android popup that asks you which app you want to launch for the peripheral that was connected, and it just seems that on some s7 software versions it's broken.
Given AFAIK it works fine on the stock Samsung international version which mine is I'd hazard a guess that those who have issues are using carrier-customized ROMs, said carriers have botched stock android functionality when inserting their awful bloatware and the responsibility's on them... make sure you're up to date in case they fixed it (or not in case they broke it recently...)
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