I have lot of articles with record image  (Pages → Databases → edit desired database → Options card → Record Image Settings section)

Directly in articles I see these images but when I see list of articles in category view, image previews are not displayed. This worked in 4.7.3 but thumbnails disappeared after upgrade to 4.7.5

Is it OK, or missing images are bug?

What listing template have you set in the database/category settings?

Default, I did not make any changes in this and I have the same issue on two different boards.

Please state the name as shown in the database settings. The default “listing” template would indeed not show the record image. It has always been this way. Only the front page of Pages databases has templates to show the the record images as part of the “article mode”. Showing the record image in listing templates would require third party templates. 

If you can provide an example for us to take a look at, we can certainly advise accordingly