Hello,
I am having random anvil offline errors as well. At first I experienced only in the IDE, but a couple of weeks ago I got some reports from my users, that the website is not working. Nowadays I can see it pop up sometimes in my logs.
I saw some threads, where others experienced the same issue, where they concluded, that some browser extension may cause the issue. So I also tried their solution out. Deleted extensions, then cookies, then basically cleaned my whole browser, but the issue remained.
The most frustrating thing is that I can not reproduce the issue. It just occurs, when a function has to call the server.
I wrote an email to support@anvil.works, hoping that we can investigate it further, unfortunately I did not receive any response.
The last time it occured, it was on 11th of July, but I can not figure out, what causes it.
Looking back at the logs, I noticed a slightly different error stating, that AppOfflineError: Connection to server failed (1006).
This issue has made some headaches, but hopefully it will be soon fixed.