I ruled out adblocker because of the safemode where it still didn’t work indeed. Maybe it was a bug in the adblocker 
But on another note I just did a test to see what I should see when safe mode is enabled now that the issue is solved, /plugins/ does not load in safe mode at all, even with adblocker disabled 
- so giving the exact same result as my screenshot above. Refreshing to exit safe mode works and plugins load instantly.