I don't make sure it is fully in the park position

Usually when I put the truck in park, it doesn't always "click" into park position. I usually have to either rock my body forcefully forward to get it to click into park or put it back in drive and edge a little forward and try putting it into park again. It is a real pain because if I don't make sure it is fully in the park position, my alarm system ends up going off full blast in the middle of the night because it clicked into park. I was just wondering what would cause it to not fully click into park. Someone told me it was something as simple as a spring but I have more faith in you guys and would like your input. Thank you so much!