Has anyone else come across this and if so, why does it happen?

A week ago I heard a rattle in the engine and then the oil pressure light came on. Stopped and checked but nothing obvious externally.
Two years ago the oil pressure light flickered when idling but nothing seemed easy to diagnose. A week or two later a lot of load banging and noise and the oil pressure light came on.

On both occasions I have taken the sump off and found and oil sprayer and bolt in the bottom of the sump. After stripping the head and removing the associated piston, last time it had overheated and shattered, also cracking the bearing strap on the con rod. This time as the con rod strap has hit the sprayer it has removed a chunk of the engine and some of the liner - it doesn't look like it will affect anything however.

Not wishing to do this again I am going to replace the three sprayers that have not already been done and put new piston rings throughout.

What I want to know however is why is it doing it? I believe the engine had a re-build a number of years ago and question whether they were never torqued up correctly.

Thoughts?

I imagine the bolts should all have a lock tab under them

Not according to the exploded diagrams I've seen but it's a fair idea. Can these be bought or do they need to be made?

I thought something was making a noise...

it'll polish out