Blurry JPEGs preview during import phase

Hello, I am struggling with an issue, when I want to import my photos. Click on Import > an Import windows shows up. I choose my folder with photos (RAFs + JPEGs for every one shot). Tha RAF previews are perfectly sharp, but the JPEG previews are blured. The problem is, when I want to choose only perfectly sharp JPEGs, I need to see the RAFs before to recognize, if the photo is correctly focused...

The checkbox "1:1 preview" is checked of course. The problem is only with JPEGs.

Thank you.