I reported this a long time ago via Discord. It's never gone away, I've just been to lazy to file this bug report before now.
I get the below warning whenever I am composing a topic on the forum.
This is a new topic so there is no way it can be open on any of my other devices.
It seems to happen a certain number of seconds after I start composing and repeats.
I just click ignore, but it is annoying.
(I have had it 9 times whilst typing this message.)
There's also this little warning triangle that appears next to the upload/preview buttons just before the warning message appears.
If I try to post or save an edit after that has appeared and before the warning message has appeared the post will get stuck in a "saving" phase and I will lose the last edit.
I am using Safari macOS right now, on iPhone I use the official DiscourseHub app. Happens in both.
FWIW I saw it once and coincidentally shortly before Matt posted this. However, I did have an open tab with a reply in-progress, so that made sense. I don't the problem on my end (with my little use of the forum) and I use the forum via a web-browser only.
This forum runs on Discord, so this buggy behaviour should be probably brought up to the Discord folk. I see that we run version 3.1.3 right now, which came out a little less than a month ago. That means our forum software is regularly updated, which means it could be a newly introduced bug/regression.
However, I also see that this issue has been reported long before too. (It doesn't mean it has been resolved, or that it hasn't come back.)
The only other thing to add is that when I'm typing i do a lot of editing (moving the cursor position and changing what has already been typed) due to mistakes and clarifying my wording, and whatever is happening whilst I'm editing seems to trigger this. If I just type and don't edit, it doesn't seem to happen. Maybe it's related to length of time typing.
And I'm wondering if the warning triangle indicates a connectivity issue, and the warning message is a false positive not really indicating the real problem?
Finally, I don't have this issue on 4 other Discourse forums I use. Which is odd.
D'oh! Of course I meant to spell it "Discourse". I did link to Discourse's GitHub and, well, Discourse, though (-:
That's a good point. It could potentially be a configuration problem then. Are those four other forums running on version 3.1.3 too? (You can see it in tag <meta name="generator"> in the page source.)