@Nicede, When performing a search on either Google or here on Discourse using ‘grav clear cache images’ you’ll find the following existing post Images deleted after Clear Cache.
The post points to the Cache configuration section of the documentation:
clear_images_by_default: By default grav will include processed images when cache clears, this can be disabled by setting this to
false
What setting is your installation using?
Note, the default behaviour has been changed from true to false in release 1.7.16. The docs however, have not been updated yet… I’ve created a PR to fix this.