blown motor

So after rebuilding my sled after 3 years of it breaking (see my long list of threads on here if you want a good story) I found out that I may need new pistons. In a previous post I mentioned I did a compression test which came back 30, 30, 120, 30. Then used a bore scope to check if the valves...

Took my apex mcypress turbo 270 hp 12 psi. For an oil change dealer didnt tighten oil drain plug one ride went Good next ride bolt fell out drained oil . Stalled towed it back ... They put new oil in it said they looked it over all good.. Next day try and ride turbo is blown.. Took it back...