Why does my transmission shit hard into 2nd if I slow down & not stopping

What is your question?

During the course of normal driving I may slow down for a red light braking slowly, however if the light turns to green & I gradually push down on the accelerator and the engines rev's and then shift hard into gear. If I am starting from a complete stop I don't have any issues, I have a smooth shift through the gears, It is only when I am driving and slow down and then attempt to take off (accelerate) in a normal speed do I experience the hard shifting.

What makes this problem better or worse?

not making a complete stop

How long has your 2015 Chevrolet Silverado 2500 HD had this problem?

2 weeks