I can't pinpoint what causes it, but it works for a while then at some random point it stops showing the above.

This is when you mouse over a ship in the fleet view port in the lower left.
It usually shows:
Class
Hit Points
Moves
Sensor Range
Logistics

At a random point it starts only showing:
Class
Sensor Range
Logistics

Completely missing the 2 most important pieces of information.
The only way to see those pieces of info is to take ships out of the fleet, view their HP / Moves, then put them back in - tedious.

Alternatively I can quit the game completely and reload it.
Although I'll usually play something else at that point as it's really annoying

It's usually at least 30 mins before it breaks I'd say.
I'm playing on a large map with 9 civs and I have 10GB of RAM (It's only using 2.1GB right now loaded up).