Just tried it after CTRL+F5, yes, unfortunately, it still does. All I tried was go to soulsdetour profile at https://ecency.com/@soulsdetour and then click on "Add to Favorites" icon several time, I always get back the same error.
We found the bug, we will fix it asap. This error apparently comes up when you already favorited account but try to favorite again.
Great seeing this and I am glad to be of help!
Keep making Ecency better!
By the way, I still see the 404 error right after publishing a new post with Ecency web, under Brave browser.
I've already reported that issue.