Can't be the cam, it has to be me?

Without any of us begin there, it sure SOUNDS like you got it right. One way to check that you advanced it: Assuming you still have the dot on the cam sprocket at 6 o'clock with #1 at TDC, then that dot now ought to be about 1/2 a tooth to the left of where it was before.

BTW, some keyways on some parts are tight, but being OK on some and not OK on others on the same part may say that the machining is poor, like having multiple bits on a machine that are not all the same size.