Braided line over rocks?

Depends on the technique you're using, it could be getting cut off by native mussels or by rough stone but you would notice a hang up prior if it was stones,  I use braided line on my heavy set ups and fish on the middle Allegheny near L/D6 and have little to no issues, and my girlfriend uses 20# Power Pro with leader and has no break/cut/rip offs and it's pretty rocky where we fish.   First main question is are you using a leader of either fluorocarbon/mono/steel/titanium?  There may ALSO be a very SMALL/SLIGHT possibility of defective product.

You can tie on a leader from 12" up to 6' or so if you don't mind casting a knot through the guides. I like a uni-uni splice for lines of similar diameter, or an improved Albright if the leader is noticeably thicker.

If it was breaking at the knot then you may want to consider a leader because the constant load on the knot could be breaking it on the back to front cast motion.  A leader (mono or fluorocarbon) will take the load better because they both stretch some adding suppression to the load.  Most line to line knots work but I found the Alberto knot to work the best only because any tension on the knot actually tightens it more, the only time I found an issue is trying to free from snags I've broken off 1 leader so far and have been using it with 8-12# leader for a while now.  I would rule out the defective spool then if it's happened out of two different spools, unless the LOT# are the same, which in that case there may be a SLIGHT chance of defect which I doubt, you would more than likely find a defect in a mono/copolymer before a braid...