I have an HP CM2320nf MFP laserjet printer. It is about 7 years old. Several months ago, copies began to appear washed out or faded down the center of the page. Shaking the black ink cartridge marginally improves the image tho it's worth it to note that the cartridge has around 40% left. The color cartridges are around 50%. I replaced the fuser but there has been no improvement.

Any ideas where I might look to correct this problem? I had tried to upload an image of a page but the upload failed. Perhaps the filesize is too large.