I've seen similar reports where prints from Adobe Elements show artifacts such as thin vertical lines, while the same image prints perfectly through Apple Photos. This often points to a driver, color management, or print settings issue rather than a problem with the Epson ET-8500 itself.
One thing to check is whether both applications are using the same color profile and print resolution settings. If Elements is managing color and the printer driver is also applying color corrections, conflicts can sometimes produce unexpected output. It may also be worth updating the Epson printer driver and testing with different print quality settings in Elements.
Since Apple Photos produces clean prints on the same printer, the hardware is likely functioning correctly.