Has it been snapping in the cast? It won't snap in the cast unless damage to a guide is quite noticeable. If you didn't find it with a stocking then it won't be damaged enough to cut your line. When it breaks is it a clean cut and does it spring back ?

What length rod are you using and what size reel?  

Does the rod run micro guides?

The reason I say this is because if the reel diameter doesn't suit the guide spacings it could be failing to clear the guides properly and there is no room for error with 1oz. 0.8 Pe doesn't take much to snap no matter what numbers they put on the packaging. It shouldnt be breaking but if you run a similar size reel from a friend on the same rod and the problem stops or persists you can say it's a fault through the rod or reel. 

Which leader knot were you using?  I used to get this now and then using a double uni knot.  Changed to FG knot and problem disappeared.

Here's an easy way to tie it. https://www.youtube.com/watch?v=52uWL43hUbw

Cheers guys. It has snapped with an FG knot but when I was using a double uni knot it was outside of the micro guides.

Flangies, I am running a 2500 Symetre with a 8' rod and when it snaps it is a clean snap sending the Richter Plug flying to South Africa.

I'm going to start using a 3/4oz plug now to be kind to the rod so hopefully this will prevent it from happening again. I'm thinking maybe it's a transportation issue and the braid is getting rubbed when I put it on my other rod for dinghy fishing creating a weak spot.

 Sounds like the small diameter line might be cutting your leader?

I had a similar problem, The line guide on my rod tip had lost its nylon bearer. So the edge was fairly sharp metal. When I cast it would score or cut the braid. I replaced the tip and all fixed.