Reconditioning was a process where First Order stormtroopers whose "programming" was deemed erratic or faulty, were subjected to a full mental wipe and reprogramming.
When Resistance spy Kazuda Xiono masqueraded as stormtrooper CS-515, the other members of "his" squad noticed his unorthodox behavior and Commander Pyre ordered him to be brought to their transport for reconditioning. Fortunately for Xiono, he was able to switch places with the real CS-515, who was taken into military custody to undergo mental reconditioning in his place.
During the Massacre at Tuanul, the stormtrooper FN-2187 was ordered by Kylo Ren to fire on civilians, but refused to follow orders. This lead to the trooper being evaluated and sent to reconditioning. However, FN-2187 deserted before the process could be carried through.
Reconditioning was first mentioned in the 2015 movie Star Wars: Episode VII The Force Awakens.
- Star Wars 100 Objects