every time your capsule dies, there is a chance you lose one level or a percentage of any of the skills you have injected. natural trained skills are safe.
example: you inject spaceship command level 1 through 5. you die and you randomly lose spaceship command level 3. you still have the others but you cannot fly anything unless you train or re-inject that skill
making injectors volatile like this will push people towards spending the time to actually train the skills, it rewards natural training and lore-wise it makes sense because those skills are not actually yours; you just took them from someone else’s brain
also you don’t need to be that dramatic with the randomness of this loss. once every 10 deaths for example. a compromise