Thumbnail viewing wrong in File Manager

I replaced a file in File Manager with a new file I uploaded with the same name, but the thumbnail image in File Manager still shows the old image.
If I click on the thumbnail to view the image it shows the correct one i.e. the image I just uploaded, but the thumbnail is still showing the old image I replaced.

This has happened to a number of files and i have to keep clicking on them to check that the latest file is the one uploaded.
I don't want to change the file name or I'll have to go and change it in all my code. Is there a way to fix this?
Thanks

Contao does not recognize that your file is a new one. What you see is the last generated thumb in system/html/. Try to clear system/html/. What version are you using? Create a ticket if necessary. Maybe contao should check the date of the thumb and check if this date is older than the originals date.

Hi, thanks for your reply, I ended up duplicating the file and deleting the original - seemed to put it right