Sherlock safe words out during normal sex (ie not during a scene). He instantly takes it back. John is surprised that the safe word is used but is even more surprised when Sherlock tries to take it back when he so clearly isn't okay.
For whatever reason Sherlock fights and runs away from John when John tries to calm him down. And he manages to lock himself in a closet (or somewhere in the house that's dark and cold) in an attempt to feel safe.
John can't get through to him straight away and Sherlock falls into subdrop.
+1 Sherlock is suffering from PTSD which gets worse over time. +100 Sherlock goes into shock. +1000 john manages to get Sherlock out and treats him +1000000 damage is done, it lasts for a long time.
Sherlock safe words out, tries to take it back, hides from John and suffers subdrop
For whatever reason Sherlock fights and runs away from John when John tries to calm him down. And he manages to lock himself in a closet (or somewhere in the house that's dark and cold) in an attempt to feel safe.
John can't get through to him straight away and Sherlock falls into subdrop.
+1 Sherlock is suffering from PTSD which gets worse over time.
+100 Sherlock goes into shock.
+1000 john manages to get Sherlock out and treats him
+1000000 damage is done, it lasts for a long time.