This is on the experimental branch 1.6 and running a local server. I was unable to access the turrets via P menu. My friend also ran into the same problem when trying to access the turrets. I've clicked on Access button and nothing happened, I was unable to get inside the turret. I cannot see through it. I also can't deploy the drone via F5 key. On Single player, it works fine. On server I cannot access the turret to aim and fire it manually. If I tried accessing it and then tried to use the drone afterward, my impression is that it looks like there's a bug involving accessing the turret that also affected the deployment of personal drone. It's as if the game thinks that I'm in the turret when I'm not. I can access cockpits of SVs and HVs even when I can't use personal drone.