The Third Sin Problem is that believers still sin … believers still need their lives cleaned up.
Only believers can act to solve Sin Problem #3.
Two visible evidences of this 3rd Sin Problem are:
While God must be a part of the solution, the believers’ good choices are crucial to the solution.
Yet, when He solves the two universal Sin problems in them, God so changes (transforms) believers
that believers are enabled to have a part in His solution to this 3rd Sin Problem, as above.
Since unbelievers are not changed as believers are, they unable to deal effectively with their sins.