2017 Buick LaCrosse, Engine/Tach surge

What is your question?

Has anyone experienced an issue with the 2017 Buick LaCrosse where at lower speeds (~35mph) the engine will rev/surge and the tachometer pegs high, but the speed doesn't change? The engine revs very high. Car was taken to the dealer but the problem, which has happened 3/4 times, cannot be duplicated at the dealership, therefore "no problem found."

What makes this problem better or worse?

not sure - happens intermittently

How long has your 2017 Buick LaCrosse had this problem?

a few months, intermittent