Solution:

The problem of a ghost image on a printed page is a failing fuser. In a printer, the toner is applied to the page. The toner and paper then go through the fuser. The fuser uses high temperature to instantly melt the toner into the page. When everything works you get clean crisp pages.

However, the fuser can fail in a couple of ways that result in two different types of “ghost images”:

The first type of ghost image may appear as sort of a fuzzy drop shadow on all text and lines. This means that the fuser is misaligned: it is fusing toner at the correct locations, but then also fusing toner a milimeter or more down the page.

The second type of ghost image may appear as a repeat of the printing several inches above, or from the previous page. This is a more severe form of misalignment where the fuser is rolling through a quarter of the page and fusing excess toner from an earlier pattern.

In either case, you should replace the fuser.  If your printer is under warranty, HP should be good enough to send you a replacement unit. Otherwise, prices between HP and 3rd party vendors and 3rd party manufacturers will vary greatly, so shop around. Fusers may be available as stand-alone units or as kits that also includes supplies and replacement rollers. Decide which is best for you. There are YouTube videos that show you how to replace the fuser yourself, which is much like replacing the toner cartridge, except the fuser is in the back of the printer.