I am having trouble maxing out the skills. I am performing the actions but my skills stopped upgrading. Health boost and health springs are stuck on 19. And everything else has stopped also. Every once and a while one will randomly upgrade. What's going on?!?
from what i've seen, 19 to 20 is the hardest one to get. it usually takes in the neighborhood of 50-100 officer deaths to get it. it's one of those things you don't try to focus on, but instead simply remember to try to get that kind of kill as you do other things. it helps your sanity far, far better if you do it that way.