I work on a website that has an Angular front end that lazy loads js chunks via webpack. Some of our users on Firefox (and only Firefox) have intermittently run into an issue where one or more of the js chunks will not load unless they clear their Firefox cache and try again, at which point Firefox will (correctly) load the previously unloaded js chunk. I've obtained HAR files from multiple affected users, and seen the pattern for myself. For example, in the screenshot I've shared, the single file shows -1 Bytes transferred, status code 0. I have suspected extension or add-on (some sort of js or ad blocker), but some affected users swear that they see the problem even when all of their extensions are disabled. Now, my best guess is some sort of issue with the caching system in Firefox itself, but really, that is just a random guess. I know, of course, that this is not enough information to debug this issue, but I hope that maybe this will ring a bell for someone, and they can point me in the right direction. Here are two discussions (on our site) where users have been reporting the issue, including with some technical details: https://boardgamegeek.com/thread/2800974/cant-open-forum-threads-firefox https://boardgamegeek.com/thread/2788693/specific-videos-page-immediately-redirects-me-empt