When a user changes the layout, they receive the following error:
"Oops...Something went wrong [...] ResizeObserver loop completed with undelivered notifications. Please try again [...]"
When the layout changes again while the frontend code is updating, then this error is generated.
It can be very difficult to avoid these errors in the code. You can click to "ok" as the error is harmless.
If the error persists, you can try clearing your web browser cache.