The File Explorer fails to render some Olympus RAW (.ORF) image files.

Oly has at least two versions of their .ORF RAW files.

File Explorer only recognizes the "old" version. E-300 - E-500 cameras.
From E-30 there is a second version (compressed). This second version is not rendered as an image in File Explorer, however it is rendered as an image in the Photos App. The "old" version is also rendered in Photos.

I'm guessing, but you may be using two different versions of the Oly RAW image Codec. Only the latest supports both RAW formats.

Or, perhaps the "Microsoft Camera codec pack" needs updating.

I'll be happy to provide samples of the two different .ORF Raw files - if required.