This month Mercenary Kings is free for PS4 if you have PS+. Since this was the case, I decided to download the game. 

The game played fine at first and had a bunch of fun with it until I encountered a game breaking bug. On the mission, the Snitch (I believe this was the name of the mission, I could be wrong) you have to capture a soldier that was in a mech to get info from him. Problem is, when I encounter the mech, the game crashes. 

I've tried to fight the mech about 5 times, and every time the game brings up an error screen saying that the game crashed. This normally wouldn't be a problem because you can play missions in any order once you unlock them, but this mission is required in order to unlock the next rank in the game.

It's clear throughout the time I played the game that the PS4 version is poorly optimized because the game has a bunch of issues other than the ones I've pointed out. I guess I'll just wait until the PS4 version is updated or when the game is significantly discounted on Steam.