Two hours of investigation wasted

A client reported that menus weren’t working – just since this morning. I spent all morning looking for the causes, when your latest update came through. And then I was able to reactivate the caching and now everything is back to normal. Comments by other posters here suggest that it has to do with js or jquery and combining js, which would explain why deactivating the cache solved the problem in the short term. But no one is going to pay me for the lost time.