Can you please help us reproduce this? Which AEM version are you on?
Is this happening for all Assets or few?
Reference Read:- Apply image presets or dynamic renditions
Link:- http://www.tothenew.com/blog/exploration-of-aem-dam/
// Custom Renditions
Access the DAM update asset model from the workflow console (classic UI view steps listed below)
Access http://<host>:<port>/libs/cq/workflow/content/console.html
- In the Models tab, double click on “DAM update asset” workflow.
- Double click to edit the 14th workstep Processing Thumbnails. In the dialog box we can see under thumbnails tab some default resolution configurations in a multi-field, to which we can add or remove our custom resolution configuration too.
- After adding the custom resolution, Click OK and save the workflow from top left and close the workflow console.
- The custom rendition of the resolution that we added will now be generated for every asset that is uploaded in DAM.
Kautuk Sahni