Hey,
850 miles on my 2015 FR-S - and first post here
I've also encountered the stiff 2nd gear.
It happens when the car is cold, especially in the morning. Goes away after a few minutes.
I've also noticed that REVing a bit higher before switching to 2nd - ~4k RPM - makes the change much smoother.
Still breaking in the engine, it'll be interesting to see if this changes after I start driving "normally".