One of the balls missing would not cause this. It's when the balls stick and can not move that would cause it.
Even though the book says 1.75 Qts, you still need to go by the full mark on the dipstick. Make sure the oil level is not over this mark.
Replacing the rings is a pretty big job. But with only 500 hours on the engine, this is actually one of the least possible issues.
What I would suggest at this point is to first check the oil level.
Then I would remove the pulse line from the fuel pump and engine, and clean it out good.
Then I would monitor it for a while.
It is possible that the crankcase had gotten overfilled at one point, or if the unit was run on a slope, it could have gotten oil into the line. Once oil gets in there, it stays until you clean it out.
If it continues to get oil in it, then you may consider having a leak down test done on it. I definitely would not go through the expense of replacing the rings without having first done a leak down test.