Most embarrassing dev moments:
Many years ago before I knew anything about javascript minification, I opened a .min.js file and thought "wow the guy who wrote this must be insanely smart"

The ability to read .min.js files

When you develop a standalone page using JS and the old JS, JQuery libraries interfere with your current libraries!
Delete
Delete
Delete
..
.
..
Open that js file rename
Open that min.js file rename
..
.
..
Still Not working!
Cleared cache ... works like a charm!
Damn you cache and min.js!!!

Just dropping some current experience here.

Content security policies are big mess in both chrome and firefox.

Chrome has some 4 years old "bug" where you can't add hash of JS file to 'style-src' policy to permit inline-styles THAT would be set by this script (jQuery actually).
Firefox is beautifully unhelpful, it just pops of error "blocked ..something..", not even saying what it was.

EDIT:
And I am missing a pair of some steel balls to ask about this on SO because there is this much of very similar questions, nonetheless -if I did read them right- every one of them is talking about enabling style attribute, and that's something different.

EDIT2: Chrome currently generates 138 errors "jquery-3.4.0.min.js:2 Refused to apply inline style..." , this ain't hitting production.