Just noticed today after going for a quick run, that one of the hardcases on my Gens Ace 3S 5000mAh 40C batteries had come undone. It was only a small amounts where it seems the battery case wouldn't 'click' back into position. I pulled the entire hardcase off to check the cells themselves and they all seemed fine; none had puffed, all nice and flat and rectangular so I figured it was just a knock the case had copped or from the way I tie the batteries down which is on a slight angle, putting pressure on one side of the case, problably pulling the other side to the point of coming apart.

So I ended up just putting the hardcase back on and using some electrical tape to get the hardcover to stay together as once removed the case didn't really seem to want to click back together itself.

I know once a battery puffs up it's time to get rid of it, but the cells seemed fine, flat and no problems there, just the cover itself.

Any reason to be concerned?

Yup a broken hard case is no issue. As long as all the cells are balancing fine and holding charge you are good to go. I've had one hardpack actually expand so much it broke apart the entire hard casing. Voltage on first cell was 8.77 and second cell was at .35 lol...needless to say it was one of the early generation Venom 2s 5000mah 20C lipos.

You could use some dbl sided tape if you wanted to make it look more like stock cases without the tape on the outside. Long as the cells are not puffed and balance, you're in good shape.