downloading images from browser sometimes results in it appearing in the wrong group, see screenshot, crdownload and tmp are all jpg's. Refreshing the folder with SET FORMAT=!folder
GO CURRENT resolves issue.
Is that with version 12.32?
Which column are you grouping by there?
I can't reproduce this so far, at least with the info we have.
A lot of the detail is missing here, though. I can't see if the files have the right extensions or not, since all the files are hidden in your first screenshot. The problem could be that the rename was missed, not that the group didn't update, from what we can see so far.