Mack Anthem door locks

Bought a 19 last week. I love the truck but I've got some door lock issues. Mostly I need to know how they are supposed to work.

Here's my issue. First, I know my passenger door actuator is out. For whatever reason Mack didn't put a manual door lock on these doors from the inside of the door so I can only lock that door with the key from the outside and get in on the driver's side and lock it (at nighttime). I'll be fixing this of course.

Second, sometimes when I'm in the truck and yank up on the driver's door handle it will not open the door, even if I didn't lock the doors with the switch when I got in. I have to unlock with the switch to open the door even if I never locked it.
Sometimes I can yank up really hard on the door handle from the inside and it will open the door, whether I locked it or not, and sometimes it won't no matter how hard and fast I yank up on the handle.
Also, I have gotten out of the truck and while fueling a couple of times WITHOUT locking a door (key in ignition, never touch lock switch) and it will lock me out. Luckily I had a spare key both times.

So, how are these doors locks SUPPOSED to work?

I hope to add keyless entry and the modules are cheap used but not sure where the module even goes or what it would take to program it. Fobs are cheap too.