Picture Gallery shows different picture in the thumbs

Hi. I'm using the standard picture gallery, that comes with the basic typolight installation. I use version 2.6.2 in this project. In some cases, when I click a thumbnail image, a different image is shown when enlarged.

I found out, that deleting the content of the system/html file fixes the problem, but can anything be done, so the thumbs are updated automatically when the pictures in the gallery are?

Any help highly appreciated.

Thumbnail generation is part of TL. It uses a cache system, which must be removed EVERYTIME you change pictures. Usually if you just add picture, you don't have to worry about this. If you keep changing the images, using the identical names, then this problem will occur, so you will have to remove the image cache system/html for these situations.