Oh boy does this post bring back some bad memories, I had a similar experience except mine ended in a destroyed engine. They were probably just lose from the oil pump manufactor (melling of mexico).
Since then I always remove the oil pump cover bolts and generously use red loctite on them. NOTE: They're usually lose or close to it.
The knocking probably was due to the loss of oil pressure, motors tend to do that when they dont have any oil pressure.
I also reccomend a great big low oil pressure warning light positioned at EYE level, another thing I learned tearing that motor up, no oil pressure kills motors in a hurry.
Goodluck, Cp