How to eliminate the ghost after updating to Mojave

Could you elaborate on the "doesn't work" comment and the screen saver?

What happens, or doesn't happen, with the screen saver?

Similar display artifacts; the text-like patterns in the left of both photos?

Always in roughly the same place?

Try booting into Safe Mode, and try an NVRAM and SMC reset, but this is looking like it might be a hardware problem and a call to Apple Support or your local preferred service provider.

• Try booting into Safe Mode, and try an NVRAM and SMC reset. See if the problem persists.
• Try installing and booting an older macOS version on an external storage device. See if that replicates this.
• Try contacting Apple support directly, or your preferred service provider.
• Consider replacing this iMac system, given the likely cost of repairs as compared with replacement.
• If you do decide for a hardware repair, consider replacing your storage with an SSD, or with a larger SSD.

I'd suspect that whatever previously happened with the display is back again.

Or whatever has happened here has become more pronounced, or has burned in.

Or install an earlier release on and booted from an external storage device, and see if that also shows the artifact.

Given the age of the system, this Mac is probably headed for replacement.

Check with Apple Support or with your preferred service provider.

I have an macbook 12 2016, and after I updated, it started to ghost the image too.