2011 2.5i Premium - hard engine braking all of the sudden…

Our 2.5i Premium has the CVT and about 145,000 miles. It has suddenly started doing something new to us… When decelerating towards a stop light, whether on the brakes or not, there’s a point in the deceleration where it feels like the transmission downshifts and starts engine braking really hard. The speed at which this occurs doesn’t seem to be consistent, and this seems like new behavior… It seems harsh and abrupt, like somebody driving a manual that shifts into first gear too soon or doesn’t know how to properly operate the clutch.

What should I look into? Is this normal?

FWIW I just replaced the radiator, thermostat, ECT sensor, and upper radiator hose. Cleaned the throttle body, did the idle relearn, and no codes are triggered. Aside from the two little CVT coolant lines going in and out of the bottom of the radiator, nothing was touched that relates to the transmission.