Hi Island bassin!
Good to know that bass are biting again at Kourris!
Anyway, regarding PowerPro, I have been using it a lot over the last few months and have never had any problems with it.
You first have to identify where exactly was the problem: Did the line break exactly at the knot? If so, then you might reconsider the knots you are using.
Did it break somewhere else? The areas you are fishing have a lot of potentially line-damaging underwater structure, especially in the form of submerged bushes and jagged-edged rocks. You need to be checking the line all the time for abrasion and re-tie often if you have even the slightest suspicion that the line might have become damaged. Braided lines are definitely tougher in such environments than mono, but they can still fray and detoriate.
Of course, it is possible that it might be the line's fault. Last March I kept breaking 20lb Fireline all the time, I even had the line break during casting. It turned out that the whole 300-yard spool was defective.
I would suggest that at home you tie the line somewhere solid and try pulling on it both steadily but also with various hard and sudden jerks, like a 5-lber would do and see what happens.
Keep up the good job...
CyBasser