Why do thumbnail links for images in Sharepoint become broken after a day?

[troku]

When an image is saved in SharePoint, I post the image thumbnail to Teams

Post a Flow Bot to Teams using "Thumbnail Large" as shown in the following figure.

Each time a file is created in Sharepoint, a message is posted to Teams.

But when I looked at the same post on Teams a day later, I couldn't see the thumbnail image.

Do thumbnail links cause broken links after a day? If you have a solution, please let me know.

*Of course I have confirmed that the original files are on SharePoint.

[FoDelement]

I have the same problem. Did you ever find a solution? 

[troku]

This problem has unfortunately not been resolved yet.
The image files do indeed exist, but for some reason, after about a day, the images are no longer visible.

[NeonThunder]

I have the same problem.  After 1 day the thumbnail image breaks.  Looking for solution also.