Violation message in DevTools

I keep getting this error repeating on one page
[Violation] 'message' handler took 11225ms
It’s not stopping the page displaying but the page does take an age to load and display.

image.png1290×463 36.7 KB

Any ideas as to what it might be?
And what I can do to speed the page up?
Can I apply Lazy Load to none image repeats?