In the user profile, Activity -> responses -> revisions or answers tab, in the list of items if you are click any user's name it will redirect to its profile page, before that it is showing an error for a less than a second.
But I didn't see any error in the console or network. The error is :
Error occurred when loading body
GIF for the same:
Update: I can see this error message in Mozilla Firefox and not in the Google Chrome.
Mozilla Firefox: 59.0b11 (64-bit)
OS: Windows 7