Error message on slide scanning

[backstory]

I am using a new Epson Expression 11000Xl for a slide scanning project. I loaded 35mm slides into the holder that came with the scanner, placed the guide up against the glass per the instructions and lined the arrows on the holder with the guide. But every time I try to scan, I get this error message: A holder is not properly placed in position on the flatbed. Please adjust. I am able to auto detect all the frames but I'm concerned this is effecting the output and quality of my scan. Can you please advise.

[LSI_Ketelhohn]

Dear user,

Did you place both film holders on the scanner?
The message also occurs when only one of the two holders is present.
In such a case you can simply ignore it.

kind regards,
Arne