It's possible you're just unlucky.

But if this keeps up, then it can't be luck. Sure, everyone turns out a lemon once in a while.

Fwiw, I have (or had) that I've actually run. (I have a handful other engines in the box that I haven't run yet)
8 OS's
9 Magnums
1 TT

And I've only ever had 1 I would call a lemon. I have had some failures, but in each case, I can say that I did something that might or might not have lead to the problem.

But, it's true that quality control does vary quite a bit with differnet makes of engine. OS is one of the best in that regard. I've had good experience with the Mags, though the carbs one the models I have do have (fixable) issues. But I've seen some pretty silly stuff with some other brands.