This achievement seems bugged, but I don't think it is. You just need to get 15 different memorable moments in one session. You can move around the map with the helicopter, crash, do whatever, but you just can't shut off the game.
Here's a list of the memorable moments I found on Reddit from u/disftactiv:
https://www.reddit.com/r/Steep/comments/5gpd1c/memorable_mom...You Proved Your Worth (Finish "First Ride Together" Tutorial)
Gold Medal Crushed
Gold First Attempt
All Time High Score (Removed in patch 1.04)
First of The Week (Removed in patch 1.04)
Daily High Score (Removed in patch 1.04)
Personal Record Beaten
Gain 25,000 Points During Game
Extreme (7)
Speed Demon
Skate On Thin Ice
World Record Cliff Jump
30 Seconds Proximity Flying in 1 Ride
Multi-Dodge (credit VanessaMagick - Steep Forums)
60m Monstrous Jump
90m High Jump (Difficult)
Freestyle (9)
2000+ Point Jump
First Double Flip
First Triple Flip
First Quad Flip
First Quintuple Flip
First 720
First 1080
First 1440
First 1800
Bone Collector (7)
My First KO
Instant KO
Stare Death In The Face
30 Second Fall
Finisher Anyway (credit TheDevilsLuck)
Bomb Attack (credit TheDevilsLuck)
Crash Test Dummy (credit TheDevilsLuck)
Exploration (4)
Safe Landing after Major Ascent
6 Minute Uninterrupted Ride
All Alps’ Points of Interest Discovered
Walk 500m Without Giving Up (credit TheDevilsLuck)
Freeride (6)
5000 Freeride Points in 1 Ride
500 Freeride Points in a Row
GoPro 30 Second Sequence
Long Ride No Crash
Stay At Max Multiplier for 2 Minutes
Hand in Hand With Another Player (credit Damirto)