If an ImageWriter II is dropped or handled roughly, the carrier shaft bushing
may break, allowing the carriage to pull away from the platen on one side.
Output looks fine on one side of the paper, but gradually fades out as it
moves to the opposite side of the paper. Adjusting the paper thickness lever
doesn't cure the problem.
The carrier shaft bushing may appear intact, but if you look closer, the two
small dimples that the shims mount to are probably fractured or broken off.
Replace the broken carrier shaft bushing (958-0006).