If you ever messed with that darned turbine compression ring seal, you'll know that it's a nasty design.
Out of all the nice Garrett (rebuild) parts, it's one of the worst - the thrust bearing come a close second.
I dunno if there is a trick to get that compression ring seal to install correctly consistently, but I haven't figured it out yet.
You got the blasted exhaust shield bell cup loose and getting in the way, and the design of the seal being square-edged don't help with it going in nicely!
If you end up tapping it in - which is the case most times - it's probably damaged from that light tapping.
I use LOTS of oil to try and get the seal to snap into place, and that causes a big smoke show on the initial start up...
This can help sometimes, but it's still not a guarantee!
Then you end up crossing your fingers that the smoke eventually clears up soon!
-Ted