A website I frequent (a Discourse forum) uses Let's Encrypt TLS certificates which are updated every two months with a valid period of three months. But the certificate information shown by Chrome says that the certificate is out-of-date and invalid. Oddly, when you click the padlock icon it does still say "Certificate (Valid)", it's only when you click on that menu item to see the certificate details that it says it's invalid. I believe this is because Discourse installs a service worker, so that loading the page doesn't actually sent an initial network request (though it does then send a request for the live data from the forum.) Here's a video with it both showing that the site is correctly secured, while the certificate is expired.
Are there any security risks with service workers and short term TLS certificates? I assume that any subsequent requests the page makes would use the current certificate. Is this really just a Chrome bug that it shows the outdated certificate?