100% was the old turbo:
https://youtube.com/shorts/A690xYoFIDI
I don't know that this would have contributed to failure, but I did notice the oil feed line adapter from my GT2260s somehow made it onto this IS38, which is pretty funny since that means it was probably on the last IS38 too. I assume the other two adapters that disappeared were on my ball bearing IS38, which is long gone.
The annoying part is I have to buy the normal length stud now, and I'm not 100% sure I have the stock turbo end of the oil return line. When I sold the GT2260s, I sent the guy the line that I had, but after seeing that adapter, I'm not sure the shop put the stock end back in or not. I *really* do not want to pull the line off to re-do it, but I did order another one just in case. It seems to fit just fine, so I dunno.
Oh well, almost done. Changed the oil, got most of the other stuff re-connected. Just waiting on a few parts like that feed line bolt before I can fire it up and do another engine flush.