If I Download a css background image of my site, changing it with GIMP (or MS paint for that matter) and re upload it, nothing will happen. Moreover, even after I delete the file from the server, the image stays online... clicking "Flush all caches" nothing happens... I also note that the image basically stays the same --- Same filename and file extension, so it's extremely wired. What would you suggest of checking?
What I already tried and didn't help:
- Turning off server external caching tool (for both static and dynamic cache).
- Turning off AdvAgg from config/development/performance/advagg (Unchecked "Enable...")
- Turning off Drupal's internal cache system.
Update: Working answer found... See below for the answer with green checkmark.