We apologize for the instability of composr.app and appreciate your patience. We are working on the statistics addon and trying to find an optimal way to store and render data. Unfortunately, we have yet to find a solution that can handle the traffic (and therefore, tens of millions of statistical records) of composr.app. We're working hard on one.
#5744 - Model should not disengage cursor focus from template editor
This is Vivaldi-specific. They have assigned a hotkey to backspace, and IMHO that is a very bad design choice by them and shouldn't be our responsibility to workaround.
https://forum.vivaldi.net/topic/39996/backspace-key-shortcut
https://forum.vivaldi.net/topic/39996/backspace-key-shortcut