Engines slowed to a stop.
 

I was playing as a ship, I had the setting on easy so had unlimited fuel.
Anyway I was part way through a mission doing well shelling and destroying enemy ships then I noticed I was slowing down.
I thought maybe I had took damage and hadn't noticed with all the excitement but no, everything seemed OK.
Eventually the ship stopped, still firing and destroying ships but no movement, I re-selected the engine options but nothing.

I exited the mission as I was a sitting duck but wondered why this happened, is it something I should or shouldn't have done?

Col.

This happened to me one time in a sub when I forgot and left the the crew at Battle Stations for far too long.

Just a thought.

Ah, now that could be it, they were on Battle stations as it was a long battle, I checked on the crew though and it showed there was crew in the engine room but maybe they were not really there if you get my meaning.

Col.

The crew would not move from the engine room or from other departments. You'd needed to check the fatigue level on each individual crew member in the boat. I suspect you would have found that every crew member was just about worn out so they just stopped working.

This is where I was puzzled, they all seemed OK, I had plenty of green in the slider type thing as well.
I've seen the crew worn out they bend over and are falling asleep, but I was playing as ship and they are a bit different or seem to be.

Col.

^This is where I'm puzzled, where and what is this green slider type thing.?

Green Slider Thingy
 

The Green Slider is to the left of each crew compartment. If you are moving crewmen to or from the deck gun you will see it move up or down.

If you're playing as a surface ship, odds are it has the left over damage zones that you can't repair.